1
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Hutskalova V, Bou Hamdan F, Sparr C. Decarboxylative Nickel- and Photoredox-Catalyzed Aminocarbonylation of (Hetero)Aryl Bromides. Org Lett 2024; 26:2768-2772. [PMID: 37796536 PMCID: PMC11020166 DOI: 10.1021/acs.orglett.3c02389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Indexed: 10/06/2023]
Abstract
An efficient methodology for the photoredox- and nickel-catalyzed aminocarbonylation of (hetero)aryl bromides was developed. The utilization of readily available oxamic acids, the application of a broadly used organic photoredox catalyst (4CzIPN), and mild reaction conditions make this transformation an appealing alternative to classical amidation procedures. The generation of carbamoyl radicals was supported by trapping reactions with a hydrogen atom transfer catalyst in the presence of D2O, yielding the deuterated formamide. The generality of this deuteration protocol was confirmed for various oxamic acids.
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Affiliation(s)
- Valeriia Hutskalova
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Farhan Bou Hamdan
- Syngenta
Crop Protection AG, Crop Protection
Research, Schaffhauserstrasse
101, CH-4332 Stein, Switzerland
| | - Christof Sparr
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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2
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Budeev A, Dong J, Häussinger D, Sparr C. Catalyst control over pentavalent stereocentres. Nat Commun 2023; 14:8013. [PMID: 38049395 PMCID: PMC10696079 DOI: 10.1038/s41467-023-43750-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 11/17/2023] [Indexed: 12/06/2023] Open
Abstract
A monumental diversity of catalytic methods imparts the ability to select one of two configurations of tetravalent stereocentres. Conversely, catalyst control over pentavalent stereocentres, where a fifth moiety bound to the central atom encodes an expanded stereochemical space, remained a challenge to be accomplished. Herein, we report the feasibility of the catalytic tractability of pentavalent stereocentres. A bifunctional iminophosphorane thiourea catalyst enables enantio- and diastereocontrol over pentavalent phosphoranes to differentiate configurationally stable enantiomers and ensembles of diastereomers which emerge together from a single stereocentre. The desired dioxophosphorane stereoisomers are obtained with excellent yield and selectivity (up to 99% yield, 96:4 e.r. and 99:1 d.r.), while stereodivergent catalysis reroutes the reaction for selective access to each of the viable stereoisomeric states of pentavalent phosphoranes. Considering the diversity of high-valent main group species, it is expected that catalyst control over pentavalent stereocentres significantly increases the synthetically addressable stereochemical space.
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Affiliation(s)
- Anton Budeev
- Department of Chemistry, University of Basel, Basel, Switzerland
| | - Jianyang Dong
- Department of Chemistry, University of Basel, Basel, Switzerland
| | | | - Christof Sparr
- Department of Chemistry, University of Basel, Basel, Switzerland.
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3
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Moser D, Schmidt TA, Sparr C. Diastereodivergent Catalysis. JACS Au 2023; 3:2612-2630. [PMID: 37885579 PMCID: PMC10598570 DOI: 10.1021/jacsau.3c00216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 09/01/2023] [Accepted: 09/06/2023] [Indexed: 10/28/2023]
Abstract
Alongside enantioselective catalysis, synthetic chemists are often confronted by the challenge of achieving catalyst control over the relative configuration to stereodivergently access desired diastereomers. Typically, these approaches iteratively or simultaneously control multiple stereogenic units for which dual catalytic methods comprising sequential, relay, and synergistic catalysis emerged as particularly efficient strategies. In this Perspective, the benefits and challenges of catalyst-controlled diastereodivergence in the construction of carbon stereocenters are discussed on the basis of illustrative examples. The concepts are then transferred to diastereodivergent catalysis for atropisomeric systems with twofold and higher-order stereogenicity as well as diastereodivergent catalyst control over E- and Z-configured alkenes.
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Affiliation(s)
| | | | - Christof Sparr
- Department of Chemistry, University
of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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4
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Pfund B, Hutskalova V, Sparr C, Wenger OS. Isoacridone dyes with parallel reactivity from both singlet and triplet excited states for biphotonic catalysis and upconversion. Chem Sci 2023; 14:11180-11191. [PMID: 37860649 PMCID: PMC10583676 DOI: 10.1039/d3sc02768f] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 09/23/2023] [Indexed: 10/21/2023] Open
Abstract
Metal-based photosensitizers commonly undergo quantitative intersystem crossing into photoactive triplet excited states. In contrast, organic photosensitizers often feature weak spin-orbit coupling and low intersystem crossing efficiencies, leading to photoactive singlet excited states. By modifying the well-known acridinium dyes, we obtained a new family of organic photocatalysts, the isoacridones, in which both singlet- and triplet-excited states are simultaneously photoactive. These new isoacridone dyes are synthetically readily accessible and show intersystem crossing efficiencies of up to 52%, forming microsecond-lived triplet excited states (T1), storing approximately 1.9 eV of energy. Their photoactive singlet excited states (S1) populated in parallel have only nanosecond lifetimes, but store ∼0.4 eV more energy and act as strong oxidants. Consequently, the new isoacridone dyes are well suited for applications requiring parallel triplet-triplet energy transfer and photoinduced electron transfer elementary steps, which have become increasingly important in modern photocatalysis. In proof-of-principle experiments, the isoacridone dyes were employed for Birch-type arene reductions and C-C couplings via sensitization-initiated electron transfer, substituting the commonly used iridium or ruthenium based photocatalysts. Further, in combination with a pyrene-based annihilator, sensitized triplet-triplet annihilation upconversion was achieved in an all-organic system, where the upconversion quantum yield correlated with the intersystem crossing quantum yield of the photosensitizer. This work seems relevant in the greater contexts of developing new applications that utilize biphotonic photophysical and photochemical behavior within metal-free systems.
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Affiliation(s)
- Björn Pfund
- Department of Chemistry, University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Valeriia Hutskalova
- Department of Chemistry, University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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5
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Moser D, Jana K, Sparr C. Atroposelective P III /P V =O Redox Catalysis for the Isoquinoline-Forming Staudinger-aza-Wittig Reaction. Angew Chem Int Ed Engl 2023; 62:e202309053. [PMID: 37486685 DOI: 10.1002/anie.202309053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/21/2023] [Accepted: 07/24/2023] [Indexed: 07/25/2023]
Abstract
Herein, we describe the feasibility of atroposelective PIII /PV =O redox organocatalysis by the Staudinger-aza-Wittig reaction. The formation of isoquinoline heterocycles thereby enables the synthesis of a broad range of valuable atropisomers under mild conditions with enantioselectivities of up to 98 : 2 e.r. Readily prepared azido cinnamate substrates convert in high yield with stereocontrol by a chiral phosphine catalyst, which is regenerated using a silane reductant under Brønsted acid co-catalysis. The reaction provides access to diversified aryl isoquinolines, as well as benzoisoquinoline and naphthyridine atropisomers. The products are expeditiously transformed into N-oxides, naphthol and triaryl phosphine variants of prevalent catalysts and ligands. With dinitrogen release and aromatization as ideal driving forces, it is anticipated that atroposelective redox organocatalysis provides access to a multitude of aromatic heterocycles with precise control over their configuration.
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Affiliation(s)
- Daniel Moser
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Kalipada Jana
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
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6
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Schmidt TA, Schumann S, Ostertag A, Sparr C. Catalyst Control over Threefold Stereogenicity: Selective Synthesis of Atropisomeric Sulfones with Stereogenic C–S Axes. Angew Chem Int Ed Engl 2023. [DOI: 10.1002/ange.202302084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Affiliation(s)
- Tanno A. Schmidt
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Stephan Schumann
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Andreas Ostertag
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Christof Sparr
- University of Basel Department of Chemistry St. Johanns-Ring 19 4056 Basel SWITZERLAND
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7
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Schmidt TA, Schumann S, Ostertag A, Sparr C. Catalyst Control over Threefold Stereogenicity: Selective Synthesis of Atropisomeric Sulfones with Stereogenic C-S Axes. Angew Chem Int Ed Engl 2023; 62:e202302084. [PMID: 36916136 DOI: 10.1002/anie.202302084] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/13/2023] [Accepted: 03/13/2023] [Indexed: 03/16/2023]
Abstract
Catalyst control over higher-order stereogenicity addresses significantly extended stereochemical space, but selective methods to govern threefold stereogenic units remained elusive. Herein, we report the stereoselective synthesis of threefold stereogenic triptycyl sulfones with atropisomerism arising from a C(sp3)-S bond. An oxidation of a stereodynamic thioether controlled by a chiral phosphoric acid catalyst allowed to selectively access enantioenriched triptycyl sulfoxides. The ensuing enantiospecific and diastereoselective catalytic oxidation to a threefold stereogenic sulfone provided overall control over the stereogenic C-S axis. All three stereoisomers were addressable with enantio- and diastereodivergence and a stereoselectivity of up to (-sc):(+sc):(ap)=94:6:<1.
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Affiliation(s)
- Tanno A Schmidt
- University of Basel: Universitat Basel, Department of Chemistry, SWITZERLAND
| | - Stephan Schumann
- University of Basel: Universitat Basel, Department of Chemistry, SWITZERLAND
| | - Andreas Ostertag
- University of Basel: Universitat Basel, Department of Chemistry, SWITZERLAND
| | - Christof Sparr
- University of Basel, Department of Chemistry, St. Johanns-Ring 19, 4056, Basel, SWITZERLAND
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8
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Abstract
Alkene metathesis catalyzed by enantiopure metal alkylidene complexes enables exceptionally versatile strategies to products with configurationally-defined stereocenters. Desymmetrization processes thereby provide reliable stereoselective routes to aliphatic structures, while the differentiation of aromatic stereogenic units remained an outstanding challenge. Herein, we describe the feasibility of alkene metathesis to catalytically control stereogenic axes by traceless arene formation. Stereodynamic trienes are selectively converted into corresponding binaphthalene atropisomers upon exposure to a chiral molybdenum catalyst. Remarkably, stereoselective arene-forming metathesis allows enantioselectivities of up to 98 : 2 e.r. and excellent yields. As the disconnection of each bond of an aromatic target is retrosynthetically conceivable, it is anticipated that forging arenes by means of stereoselective metathesis will enable versatile approaches for the synthesis of a broad range of molecular topologies with precisely defined configuration.
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Affiliation(s)
- Zlatko Jončev
- Department of Chemistry, University of Basel, Johanns-Ring 19, 4056, Basel, Switzerland.,NCCR Molecular Systems Engineering, BPR 1095, Mattenstrasse 24a, 4058, Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel, Johanns-Ring 19, 4056, Basel, Switzerland.,NCCR Molecular Systems Engineering, BPR 1095, Mattenstrasse 24a, 4058, Basel, Switzerland
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9
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Hutskalova V, Sparr C. Control over Stereogenic N–N Axes by Pd-catalyzed 5-endo-Hydroaminocyclisations. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/a-1993-6899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A novel approach for the stereoselective construction of N–N atropisomeric compounds by a Pd-catalyzed 5-endo-hydroamino-cyclisation is described herein. A broad range of bisheterocycles connected by a configurationally stable N–N stereogenic axis was prepared with catalyst control in enantioenriched form.
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Affiliation(s)
| | - Christof Sparr
- Department of Chemistry, Universitat Basel, Basel, Switzerland
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10
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Schmidt TA, Sparr C. Photocatalytic deracemisation of cobalt(III) complexes with fourfold stereogenicity. Chem Commun (Camb) 2022; 58:12172-12175. [PMID: 36254723 PMCID: PMC9623447 DOI: 10.1039/d2cc05196f] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 10/05/2022] [Indexed: 08/25/2023]
Abstract
The deracemisation of fourfold stereogenic cobalt(III) diketonates with a chiral photocatalyst is described. With only 0.5 mol% menthyl Ru(bpy)32+ photocatalyst, an enantiomeric enrichment of up to 88 : 12 e.r. was obtained for the major meridional diastereomers. Moreover, a distribution of configurationally stable diastereomers distinct from the thermodynamic ratio was observed upon reaching the photostationary state.
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Affiliation(s)
- Tanno A Schmidt
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, Basel CH-4056, Switzerland.
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, Basel CH-4056, Switzerland.
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11
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Jončev Z, Sparr C. Atroposelective Arene‐Forming Alkene Metathesis. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202211168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Zlatko Jončev
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Christof Sparr
- University of Basel Department of Chemistry St. Johanns-Ring 19 4056 Basel SWITZERLAND
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12
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Dong J, Ostertag A, Sparr C. o‐Quinodimethane Atropisomers: Enantioselective Synthesis and Stereospecific Transformation. Angew Chem Int Ed Engl 2022; 61:e202212627. [PMID: 36256547 PMCID: PMC10100317 DOI: 10.1002/anie.202212627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Indexed: 11/07/2022]
Abstract
o-Quinodimethanes have remarkable utility as reactive intermediates in Diels-Alder reactions, enabling significantly accelerated routes to complex polycyclic compounds. The discovery of different discrete precursors to thermally generate o-quinodimethanes thereby greatly augmented their availability and versatility. However, due to the required high temperatures and the immense reactivity of o-quinodimethanes, stereoselectivity to afford isomerically defined products still constitutes a critical challenge. Herein, we describe the accessibility of atropisomeric o-quinodimethanes, the enantioselective synthesis of their precursors, their remarkable configurational stability and the stereospecific transformation by the benzannulation of dienophiles. A catalyst-stereocontrolled [2+2+2] cycloaddition, the generation of o-quinodimethane atropisomers and ensuing stereospecific Diels-Alder reactions enabled enantioselectivities through these transient intermediates with of up to 96 : 4 e.r.
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Affiliation(s)
- Jianyang Dong
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Andreas Ostertag
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Christof Sparr
- University of Basel Department of Chemistry St. Johanns-Ring 19 4056 Basel SWITZERLAND
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13
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Wu X, Malinčík J, Prescimone A, Sparr C. X‐Ray Crystallographic Studies of Quasi‐Racemates for Absolute Configuration Determinations. Helv Chim Acta 2022. [DOI: 10.1002/hlca.202200117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Xingxing Wu
- Department of Chemistry University of Basel St. Johanns-Ring 19 CH-4056 Basel Switzerland
| | - Juraj Malinčík
- Department of Chemistry University of Basel St. Johanns-Ring 19 CH-4056 Basel Switzerland
| | - Alessandro Prescimone
- Department of Chemistry University of Basel, BPR 1096 Mattenstrasse 24a, CH-4058 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 CH-4056 Basel Switzerland
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14
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Dong J, Ostertag A, Sparr C. o‐Quinodimethane Atropisomers: Enantioselective Synthesis and Stereospecific Transformation. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202212627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Jianyang Dong
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Andreas Ostertag
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Christof Sparr
- University of Basel Department of Chemistry St. Johanns-Ring 19 4056 Basel SWITZERLAND
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15
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Jakobi M, Sparr C. Streamlined Synthesis of Aminoacridinium Photocatalysts with Improved Photostability. Org Process Res Dev 2022. [DOI: 10.1021/acs.oprd.2c00209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Markus Jakobi
- Department of Chemistry University of Basel, 4056 Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel, 4056 Basel, Switzerland
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16
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Jakobi M, Zilate B, Sparr C. Synthesis of Diarylaminoacridinium Photocatalysts by Halogen‐Metal Exchange Combined with Directed <i>ortho</i> Metalations. Adv Synth Catal 2022. [DOI: 10.1002/adsc.202200819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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17
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Moser D, Sparr C. Synthesis of Atropisomeric Two‐Axis Systems by the Catalyst‐Controlled
syn
‐ and
anti
‐Selective Arene‐Forming Aldol Condensation. Angew Chem Int Ed Engl 2022; 61:e202202548. [PMID: 35343034 PMCID: PMC9322266 DOI: 10.1002/anie.202202548] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Indexed: 12/21/2022]
Abstract
Simultaneous control over the configuration of multiple stereocenters is accomplished by numerous catalytic methods, providing a reliable basis for the synthesis of stereochemically complex targets in isomerically defined form. In contrast, addressing the configurations of multiple stereogenic axes with diastereodivergent catalyst control is thus far only possible by stepwise approaches. Herein we now describe that all four stereoisomers of atropisomeric two‐axis systems are directly tractable by assembling a central aromatic unit of teraryls through an arene‐forming aldol condensation. By using cinchona alkaloid‐based ion‐pairing catalysts, the four feasible reaction pathways are differentiated from identical substrates under defined basic conditions without preactivation, thus enabling complete stereodivergence with enantioselectivities of up to 99 : 1 e.r.
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Affiliation(s)
- Daniel Moser
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
- NCCR Molecular Systems Engineering BPR 1095 Mattenstrasse 24a 4058 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
- NCCR Molecular Systems Engineering BPR 1095 Mattenstrasse 24a 4058 Basel Switzerland
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18
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Wu X, Sparr C. Stereoselective Synthesis of Atropisomeric Acridinium Salts by the Catalyst‐Controlled Cyclization of
ortho
‐Quinone Methide Iminiums. Angew Chem Int Ed Engl 2022; 61:e202201424. [PMID: 35167176 PMCID: PMC9306694 DOI: 10.1002/anie.202201424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Indexed: 11/07/2022]
Abstract
Quinone methides are fundamental intermediates for a wide range of reactions in which catalyst stereocontrol is often achieved by hydrogen bonding. Herein, we describe the feasibility of an intramolecular Friedel–Crafts 6π electrocyclization through ortho‐quinone methide iminiums stereocontrolled by a contact ion pair. A disulfonimide catalyst activates racemic trichloroacetimidate substrates and imparts stereocontrol in the cyclization step, providing a new avenue for selective ortho‐quinone methide iminium functionalization. A highly stereospecific oxidation readily transforms the enantioenriched acridanes into rotationally restricted acridiniums. Upon ion exchange, the method selectively affords atropisomeric acridinium tetrafluoroborate salts in high yields and an enantioenrichment of up to 93 : 7 e.r. We envision that ion‐pairing catalysis over ortho‐quinone methide iminiums enables the selective synthesis of a diversity of heterocycles and aniline derivatives with distinct stereogenic units.
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Affiliation(s)
- Xingxing Wu
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
- NCCR Molecular Systems Engineering, BPR 1095Mattenstrasse 24a4058BaselSwitzerland
| | - Christof Sparr
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
- NCCR Molecular Systems Engineering, BPR 1095Mattenstrasse 24a4058BaselSwitzerland
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19
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Moser D, Sparr C. Synthesis of Atropisomeric Two‐Axis Systems by the Catalyst‐ Controlled syn‐ and anti‐Selective Arene‐Forming Aldol Condensation. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202202548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Daniel Moser
- University of Basel: Universitat Basel Department of Chemistry SWITZERLAND
| | - Christof Sparr
- University of Basel Department of Chemistry St. Johanns-Ring 19 4056 Basel SWITZERLAND
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20
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Wu X, Sparr C. Stereoselective Synthesis of Atropisomeric Acridinium Salts by the Catalyst‐Controlled Cyclization of
ortho
‐Quinone Methide Iminiums. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202201424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Xingxing Wu
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
- NCCR Molecular Systems Engineering, BPR 1095 Mattenstrasse 24a 4058 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
- NCCR Molecular Systems Engineering, BPR 1095 Mattenstrasse 24a 4058 Basel Switzerland
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21
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Wu X, Sparr C. Retrosynthetic polyketide disconnections for unnatural aromatics. Trends in Chemistry 2022. [DOI: 10.1016/j.trechm.2022.01.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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22
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Hutskalova V, Prescimone A, Sparr C. Synthesis of Helical and Planar Extended‐Phenanthridinium Salts. Helv Chim Acta 2021. [DOI: 10.1002/hlca.202100182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Valeriia Hutskalova
- Department of Chemistry University of Basel St. Johanns-Ring 19 CH-4056 Basel Switzerland
| | - Alessandro Prescimone
- Department of Chemistry University of Basel BPR 1096 Mattenstrasse 24a CH-4058 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 CH-4056 Basel Switzerland
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23
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Affiliation(s)
- Tanno A. Schmidt
- Department Chemie Universität Basel St. Johanns-Ring 19 4056 Basel Schweiz
| | - Christof Sparr
- Department Chemie Universität Basel St. Johanns-Ring 19 4056 Basel Schweiz
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24
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Abstract
Overcrowded alkenes are expeditiously prepared by the versatile Barton-Kellogg olefination and have remarkable applications as functional molecules owing to their unique stereochemical features. The induced stereodynamics thereby enable the controlled motion of molecular switches and motors, while the high configurational stability prevents undesired isomeric scrambling. Bistricyclic aromatic enes are prototypical overcrowded alkenes with outstanding stereochemical properties, but their stereocontrolled preparation was thus far only feasible in stereospecific reactions and with chiral auxiliaries. Herein we report that direct catalyst control is achieved by a stereoselective Barton-Kellogg olefination with enantio- and diastereocontrol for various bistricyclic aromatic enes. Using Rh2 (S-PTAD)4 as catalyst, several diazo compounds were selectively coupled with a thioketone to give one of the four anti-folded overcrowded alkene stereoisomers upon reduction. Complete stereodivergence was reached by catalyst control in combination with distinct thiirane reductions to provide all four stereoisomers with e.r. values of up to 99:1. We envision that this strategy will enable the synthesis of topologically unique overcrowded alkenes for functional materials, catalysis, energy- and electron transfer, and bioactive compounds.
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Affiliation(s)
- Tanno A. Schmidt
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - Christof Sparr
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
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25
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Scherrer D, Vogel D, Drechsler U, Olziersky A, Sparr C, Mayor M, Lörtscher E. Reaktionsverfolgung von Festphasensynthesen in selbstassemblierenden Monolagen mit oberflächenverstärkter Raman‐Spektroskopie. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Dominik Scherrer
- Science and Technology Department, IBM Research Europe Säumerstrasse 4 8803 Rüschlikon Schweiz
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Schweiz
| | - David Vogel
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Schweiz
| | - Ute Drechsler
- Science and Technology Department, IBM Research Europe Säumerstrasse 4 8803 Rüschlikon Schweiz
| | - Antonis Olziersky
- Science and Technology Department, IBM Research Europe Säumerstrasse 4 8803 Rüschlikon Schweiz
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Schweiz
| | - Marcel Mayor
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Schweiz
- Institute for Nanotechnology (INT) Karlsruhe Institute of Technology (KIT) P. O. Box 3640 76021 Karlsruhe Deutschland
- Lehn Institute of Functional Materials (LIFM) School of Chemistry Sun Yat-Sen University (SYSU) Guangzhou 510275 VR China
| | - Emanuel Lörtscher
- Science and Technology Department, IBM Research Europe Säumerstrasse 4 8803 Rüschlikon Schweiz
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26
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Scherrer D, Vogel D, Drechsler U, Olziersky A, Sparr C, Mayor M, Lörtscher E. Monitoring Solid-Phase Reactions in Self-Assembled Monolayers by Surface-Enhanced Raman Spectroscopy. Angew Chem Int Ed Engl 2021; 60:17981-17988. [PMID: 34048139 PMCID: PMC8456949 DOI: 10.1002/anie.202102319] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 05/18/2021] [Indexed: 12/27/2022]
Abstract
Nanopatterned surfaces enhance incident electromagnetic radiation and thereby enable the detection and characterization of self-assembled monolayers (SAMs), for instance in surface-enhanced Raman spectroscopy (SERS). Herein, Au nanohole arrays, developed and characterized as SERS substrates, are exemplarily used for monitoring a solid-phase deprotection and a subsequent copper(I)-catalyzed azide-alkyne cycloaddition "click" reaction, performed directly on the corresponding SAMs. The SERS substrate was found to be highly reliable in terms of signal reproducibility and chemical stability. Furthermore, the intermediates and the product of the solid-phase synthesis were identified by SERS. The spectra of the immobilized compounds showed minor differences compared to spectra of the microcrystalline solids. With its uniform SERS signals and the high chemical stability, the platform paves the way for monitoring molecular manipulations in surface functionalization applications.
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Affiliation(s)
- Dominik Scherrer
- Science and Technology Department, IBM Research EuropeSäumerstrasse 48803RüschlikonSwitzerland
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - David Vogel
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - Ute Drechsler
- Science and Technology Department, IBM Research EuropeSäumerstrasse 48803RüschlikonSwitzerland
| | - Antonis Olziersky
- Science and Technology Department, IBM Research EuropeSäumerstrasse 48803RüschlikonSwitzerland
| | - Christof Sparr
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
| | - Marcel Mayor
- Department of ChemistryUniversity of BaselSt. Johanns-Ring 194056BaselSwitzerland
- Institute for Nanotechnology (INT)Karlsruhe Institute of Technology (KIT)P. O. Box 364076021KarlsruheGermany
- Lehn Institute of Functional Materials (LIFM)School of ChemistrySun Yat-Sen University (SYSU)Guangzhou510275P.R. China
| | - Emanuel Lörtscher
- Science and Technology Department, IBM Research EuropeSäumerstrasse 48803RüschlikonSwitzerland
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27
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Triandafillidi I, Kokotou MG, Lotter D, Sparr C, Kokotos CG. Aldehyde-catalyzed epoxidation of unactivated alkenes with aqueous hydrogen peroxide. Chem Sci 2021; 12:10191-10196. [PMID: 34377408 PMCID: PMC8336450 DOI: 10.1039/d1sc02360h] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/18/2021] [Indexed: 12/23/2022] Open
Abstract
The organocatalytic epoxidation of unactivated alkenes using aqueous hydrogen peroxide provides various indispensable products and intermediates in a sustainable manner. While formyl functionalities typically undergo irreversible oxidations when activating an oxidant, an atropisomeric two-axis aldehyde capable of catalytic turnover was identified for high-yielding epoxidations of cyclic and acyclic alkenes. The relative configuration of the stereogenic axes of the catalyst and the resulting proximity of the aldehyde and backbone residues resulted in high catalytic efficiencies. Mechanistic studies support a non-radical alkene oxidation by an aldehyde-derived dioxirane intermediate generated from hydrogen peroxide through the Payne and Criegee intermediates.
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Affiliation(s)
- Ierasia Triandafillidi
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens Panepistimiopolis 15771 Athens Greece
- Department of Chemistry, University of Basel St. Johanns-Ring 19 Basel 4056 Switzerland
| | - Maroula G Kokotou
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens Panepistimiopolis 15771 Athens Greece
| | - Dominik Lotter
- Department of Chemistry, University of Basel St. Johanns-Ring 19 Basel 4056 Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel St. Johanns-Ring 19 Basel 4056 Switzerland
| | - Christoforos G Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens Panepistimiopolis 15771 Athens Greece
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28
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Sparr C, Hutskalova V. The Versatility of the Aryne–Imine–Aryne Coupling for the Synthesis of Acridinium Photocatalysts. Synlett 2021. [DOI: 10.1055/s-0040-1720349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
AbstractThe increasing use of acridinium photocatalysts as sustainable alternative to precious metal-based counterparts encourages the design and efficient synthesis of distinct catalyst structures. Herein, we report our exploration of the scope of the aryne–imine–aryne coupling reaction combined with a subsequent acridane oxidation for a short two-step approach towards various acridinium salts. The photophysical properties of the novel photocatalysts were investigated and the practical value was demonstrated by a cation-radical accelerated nucleophilic aromatic substitution reaction.
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29
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Wellauer J, Miladinov D, Buchholz T, Schütz J, Stemmler RT, Medlock JA, Bonrath W, Sparr C. Organophotocatalytic Aerobic Oxygenation of Phenols in a Visible-Light Continuous-Flow Photoreactor. Chemistry 2021; 27:9748-9752. [PMID: 33871915 DOI: 10.1002/chem.202101313] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Indexed: 11/11/2022]
Abstract
A mild photocatalytic phenol oxygenation enabled by a continuous-flow photoreactor using visible light and pressurized air is described herein. Products for wide-ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p-quinols contributes to sustainable synthesis.
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Affiliation(s)
- Joël Wellauer
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Dragan Miladinov
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Thomas Buchholz
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Jan Schütz
- DSM Nutritional Products Ltd., P.O. Box 2676, 4002, Basel, Switzerland
| | - René T Stemmler
- DSM Nutritional Products Ltd., P.O. Box 2676, 4002, Basel, Switzerland
| | | | - Werner Bonrath
- DSM Nutritional Products Ltd., P.O. Box 2676, 4002, Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
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30
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Abstract
The steadily growing interest in substituting precious-metal photoredox catalysts with organic surrogates is vibrantly sustained by emerging methodologies to vary their photochemical behavior. Herein, we report an ad hoc approach for the preparation of acridinium salts with a particularly broad range of photoredox properties. The method involves an aryne-imine-aryne coupling to a linchpin tetrafluoro acridinium salt for a late-stage diversification by nucleophilic aromatic substitution reactions to form diaminoacridinium and undescribed aza-rhodol photocatalysts. The different functionalities and redox properties of the organic acridinium photocatalysts render them suitable for bifunctional photoredox catalysis and organocatalytic photochemical C-N cross-couplings.
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Affiliation(s)
- Valeriia Hutskalova
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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31
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Abstract
Contradictory to the first intuitive impression that forging putatively flat aromatic rings evades stereoisomerism, a striking variety of atropisomeric compounds are conceivable by the formation of arenes, offering captivating avenues for catalyst-controlled stereoselective strategies. Since the assembled atropisomeric products that contain one or several rotationally restricted single bonds are characterized by especially well defined molecular architectures, they are distinctly suitable for numerous pertinent applications. In view of the fascinating arene-forming aldol condensation pathways taking place in polyketide biosynthesis (cyclases/aromatases (CYC/ARO)), the versatile small-molecule-catalyzed aldol reaction appeared as an exceptionally appealing synthetic means to prepare various unexplored atropisomeric compounds in our efforts presented herein. In our initial studies, the use of secondary amine organocatalysts provided excellent selectivities in stereoselective arene-forming aldol condensations for a broad range of atropisomeric products, such as biaryls and rotationally restricted aromatic amides. In further analogy to polyketide biosynthesis, it was also conceivable that several aromatic rings are formed in catalytic cascade reactions. The use of small-molecule catalysts thereby enabled us to transfer this concept to the conversion of unnatural and noncanonical polyketide substrates, thus giving access to atropisomers with particular value for synthetic applications. The versatility of the stereoselective aldol reactions with numerous catalytic activation modes further provided a strategy to individually control several stereogenic axes, similar to the various methodologies developed for controlling stereocenter configurations. By the use of iterative building block additions combined with catalyst-controlled aldol reactions to form the aromatic rings, stereodivergent pathways for catalyst-substrate-matched and -mismatched products were obtained. Besides secondary amines, cinchona-alkaloid-based quaternary ammonium salts also proved to be highly efficient in overcoming severe substrate bias. The obtained atropisomeric multiaxis systems, with all of the biaryl bonds suitably restricted in rotation even at high temperatures, are spatially distinctly defined. The helical secondary structure is therefore excellently suited for several captivating applications.While previous catalyst-controlled stereoselective methods distinguish two stereoisomers for each stereogenic unit, catalyst control beyond the realms of this dualistic stereoisomerism remained unexplored. By the selective preparation of O̅ki atropisomers characterized by their sixfold stereogenicity in Rh-catalyzed [2 + 2 + 2] cyclotrimerizations, one out of the six possible stereoisomers resulting from the restricted rotation of a single bond was shown to be catalytically addressable. Catalyst control over higher-order stereogenicity therefore further interconnects conformational analysis and stereoselective catalysis and offers captivating avenues to explore uncharted stereochemical space for creating a broad range of unprecedented molecular motifs.
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Affiliation(s)
- Tanno A. Schmidt
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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32
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Raps FC, Fäseke VC, Häussinger D, Sparr C. Catalyst‐Controlled Transannular Polyketide Cyclization Cascades: Selective Folding of Macrocyclic Polyketides. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202005733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Felix C. Raps
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Vincent C. Fäseke
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Daniel Häussinger
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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33
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Moser D, Castrogiovanni A, Lotter D, Witzig RM, Fäseke VC, Raps FC, Sparr C. Catalytic Cascade Reactions Inspired by Polyketide Biosynthesis. Chimia (Aarau) 2020; 74:699-703. [PMID: 32958107 DOI: 10.2533/chimia.2020.699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Aldol reactions belong to the most important methods for carbon-carbon bond formation and are also involved in one of the most astonishing biosynthetic processes: the biosynthesis of polyketides governed by an extraordinarily sophisticated enzymatic machinery. In contrast to the typical linear or convergent strategies followed in chemical synthesis, this late-stage catalysis concept allows Nature to assemble intermediates that are diversified into a broad range of scaffolds, which assume various crucial biological functions. To transfer this concept to small-molecule catalysis to access products beyond the natural systems, a stepwise approach to differentiate increasingly complex substrates was followed by investigating arene-forming polyketide cyclizations. An outline of our efforts to develop and apply these concepts are presented herein.
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Affiliation(s)
- Daniel Moser
- University of Basel, Department of Chemistry, St. Johanns-Ring 19, CH-4056 Basel
| | | | - Dominik Lotter
- University of Basel, Department of Chemistry, St. Johanns-Ring 19, CH-4056 Basel
| | - Reto M Witzig
- University of Basel, Department of Chemistry, St. Johanns-Ring 19, CH-4056 Basel
| | - Vincent C Fäseke
- University of Basel, Department of Chemistry, St. Johanns-Ring 19, CH-4056 Basel
| | - Felix C Raps
- University of Basel, Department of Chemistry, St. Johanns-Ring 19, CH-4056 Basel
| | - Christof Sparr
- University of Basel, Department of Chemistry, St. Johanns-Ring 19, CH-4056 Basel;,
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34
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Raps FC, Fäseke VC, Häussinger D, Sparr C. Catalyst‐Controlled Transannular Polyketide Cyclization Cascades: Selective Folding of Macrocyclic Polyketides. Angew Chem Int Ed Engl 2020; 59:18390-18394. [DOI: 10.1002/anie.202005733] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Indexed: 11/09/2022]
Affiliation(s)
- Felix C. Raps
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Vincent C. Fäseke
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Daniel Häussinger
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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35
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Castrogiovanni A, Lotter D, Bissegger FR, Sparr C. JoyaPhos: An Atropisomeric Teraryl Monophosphine Ligand. Chemistry 2020; 26:9864-9868. [DOI: 10.1002/chem.202001269] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 04/17/2020] [Indexed: 12/17/2022]
Affiliation(s)
| | - Dominik Lotter
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Fabian R. Bissegger
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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36
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Fäseke VC, Raps FC, Sparr C. Polyketide Cyclizations for the Synthesis of Polyaromatics. Angew Chem Int Ed Engl 2020; 59:6975-6983. [DOI: 10.1002/anie.201911255] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 11/05/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Vincent C. Fäseke
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Felix C. Raps
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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37
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Affiliation(s)
- Vincent C. Fäseke
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Felix C. Raps
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry University of Basel St. Johanns-Ring 19 4056 Basel Switzerland
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38
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Bourgeois F, Medlock JA, Bonrath W, Sparr C. Catalyst Repurposing Sequential Catalysis by Harnessing Regenerated Prolinamide Organocatalysts as Transfer Hydrogenation Ligands. Org Lett 2020; 22:110-115. [PMID: 31833781 DOI: 10.1021/acs.orglett.9b04033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A catalyst repurposing strategy based on a sequential aldol addition and transfer hydrogenation giving access to enantiomerically enriched α-hydroxy-γ-butyrolactones is described. The combination of a stereoselective, organocatalytic step, followed by an efficient catalytic aldehyde reduction induces an ensuing lactonization to provide enantioenriched butyrolactones from readily available starting materials. By capitalizing from the capacity of prolineamides to act as both an organocatalyst and a transfer hydrogenation ligand, catalyst repurposing allowed the development of an operationally simple, economic, and efficient sequential catalysis approach.
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Affiliation(s)
- Frederic Bourgeois
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | | | - Werner Bonrath
- DSM Nutritional Products Ltd. , P.O. Box 2676, 4002 Basel , Switzerland
| | - Christof Sparr
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
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39
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Witzig RM, Sparr C. Synthesis of Enantioenriched Tetra-ortho-3,3′-substituted Biaryls by Small-Molecule-Catalyzed Noncanonical Polyketide Cyclizations. Synlett 2020. [DOI: 10.1055/s-0039-1690215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The arene-forming aldol condensation is a fundamental reaction in the biosynthesis of aromatic polyketides. Precisely controlled by the polyketide synthases, the highly reactive poly-β-carbonyl substrates are diverged into numerous aromatic natural products by selective cyclization reactions; a fascinating biosynthetic strategy that sparked our interest to investigate atroposelective aldol condensations. In this Account, we contextualize and highlight the ability of small-molecule catalysts to selectively convert noncanonical hexacarbonyl substrates in a double arene-forming aldol condensation resulting in the atroposelective synthesis of tetra-ortho-3,3′-substituted biaryls. The hexacarbonyl substrates were obtained by a fourfold ozonolysis enabling a late-stage introduction of all carbonyl functions in one step. Secondary amine catalysts capable of forming an extended hydrogen-bonding network triggered the noncanonical polyketide cyclization in order to form valuable biaryls in high yields and with stereocontrol of up to 98:2 er.1 Biosynthesis of Aromatic Polyketides2 Rotationally Restricted Aromatic Polyketides3 3,3′-Substituted Binaphthalenes in Catalysis4 Stereoselective Synthesis of Atropisomers5 Synthesis of Enantioenriched Tetra-ortho-3,3′-Substituted Biaryls by the Atroposelective Arene-Forming Aldol Condensation6 Conclusion
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40
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Abstract
Recent developments in preparative photocatalysis have reshaped synthetic strategies and now represent an integral part of current organic chemistry. Due to their favourable electrochemical and photophysical properties, the nowadays most frequently used photocatalysts are based on precious Ru- and Ir-polypyridyl complexes. Apart from that, organic catalysts such as the acridinium salts are now commonly employed to complement transition metals to provide potentially sustainable strategies amenable to large-scale synthesis. In this feature article, the design, synthesis and application of aminoacridinium photoredox catalysts as well as their exceptionally broad range of redox properties are highlighted. Due to their modularity, this burgeoning class of organophotocatalysts is anticipated to contribute significantly to synthetic methodology development and the translation to a wide range of innovative implementations.
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Affiliation(s)
- Bouthayna Zilate
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, CH-4056, Basel, Switzerland.
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41
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Castrogiovanni A, Herr P, Larsen CB, Guo X, Sparr C, Wenger OS. Shortcuts for Electron-Transfer through the Secondary Structure of Helical Oligo-1,2-Naphthylenes. Chemistry 2019; 25:16748-16754. [PMID: 31674695 DOI: 10.1002/chem.201904771] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 10/30/2019] [Indexed: 01/24/2023]
Abstract
Atropisomeric 1,2-naphthylene scaffolds provide access to donor-acceptor compounds with helical oligomer-based bridges, and transient absorption studies revealed a highly unusual dependence of the electron-transfer rate on oligomer length, which is due to their well-defined secondary structure. Close noncovalent intramolecular contacts enable shortcuts for electron transfer that would otherwise have to occur over longer distances along covalent pathways, reminiscent of the behavior seen for certain proteins. The simplistic picture of tube-like electron transfer can describe this superposition of different pathways including both the covalent helical backbone, as well as noncovalent contacts, contrasting the wire-like behavior reported many times before for more conventional molecular bridges. The exquisite control over the molecular architecture, achievable with the configurationally stable and topologically defined 1,2-naphthylene-based scaffolds, is of key importance for the tube-like electron transfer behavior. Our insights are relevant for the emerging field of multidimensional electron transfer and for possible future applications in molecular electronics.
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Affiliation(s)
| | - Patrick Herr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Christopher B Larsen
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Xingwei Guo
- Current address: Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing, 100084, P.R. China
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
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42
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Affiliation(s)
- Christian Fischer
- Department of Chemistry, University of Basel, Basel CH-4056, Switzerland
| | - Christoph Kerzig
- Department of Chemistry, University of Basel, Basel CH-4056, Switzerland
| | - Bouthayna Zilate
- Department of Chemistry, University of Basel, Basel CH-4056, Switzerland
| | - Oliver S. Wenger
- Department of Chemistry, University of Basel, Basel CH-4056, Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel, Basel CH-4056, Switzerland
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43
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Abstract
The continuous development of photocatalytic methods incentivizes the design of organic catalysts to complement the frequently used and precious polypyridyl transition metal systems. Herein, a scalable synthesis of suitable acridinium dyes and their application in photoredox deuterations are described. The acridinium catalysts, prepared on multi-gram scale, allowed the deuteration of a pharmaceutically relevant scaffold in high yield and selectivity under mild conditions.
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44
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Abstract
Mimicking an enzyme's exquisite activity and selectivity is a long-standing goal for sustainable chemical method development in aqueous media. The use of interface-rich aqueous systems, such as single-chain polymers, micelles and vesicle membranes recently emerged as strategy to emulate the compartmentalization of natural systems. In aqueous solution, aggregates such as micelles or microemulsion droplets are formed, providing reaction environments different from bulk solutions that frequently improve selectivity and accelerate reaction rates for a wide array of chemical transformations. We present here selected examples of interface-rich aqueous systems and discuss the advantages they offer for chemical synthesis. In particular metal-catalyzed cross-coupling reactions are highlighted and future challenges to perform reactions in interface-rich aqueous media are discussed.
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Affiliation(s)
- Dainis Kaldre
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, CH-4056 Basel
| | - Fabrice Gallou
- Chemical & Analytical Development, Novartis Pharma AG, CH-4056 Basel
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, CH-4056 Basel;,
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Affiliation(s)
- Markus Jakobi
- Chemical & Analytical DevelopmentNovartis Pharma AG CH-4056 Basel Switzerland
- Department of ChemistryUniversity of Basel St. Johanns-Ring 19 CH-4056 Basel Switzerland
| | - Fabrice Gallou
- Chemical & Analytical DevelopmentNovartis Pharma AG CH-4056 Basel Switzerland
| | - Christof Sparr
- Department of ChemistryUniversity of Basel St. Johanns-Ring 19 CH-4056 Basel Switzerland
| | - Michael Parmentier
- Chemical & Analytical DevelopmentNovartis Pharma AG CH-4056 Basel Switzerland
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Grogg M, Hilvert D, Ebert MO, Beck AK, Seebach D, Kurth F, Dittrich PS, Sparr C, Wittlin S, Rottmann M, Mäser P. Cell Penetration, Herbicidal Activity, and in-vivo-Toxicity of Oligo-Arginine Derivatives and of Novel Guanidinium-Rich Compounds Derived from the Biopolymer Cyanophycin. Helv Chim Acta 2018; 101. [PMID: 30905972 DOI: 10.1002/hlca.201800112] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Oligo-arginines are thoroughly studied cell-penetrating peptides (CPPs, Figures 1 and 2). Previous in-vitro investigations with the octaarginine salt of the phosphonate fosmidomycin (herbicide and anti-malaria drug) have shown a 40-fold parasitaemia inhibition with P. falciparum, compared to fosmidomycin alone (Figure 3). We have now tested this salt, as well as the corresponding phosphinate salt of the herbicide glufosinate, for herbicidal activity with whole plants by spray application, hoping for increased activities, i.e. decreased doses. However, both salts showed low herbicidal activity, indicating poor foliar uptake (Table 1). Another pronounced difference between in-vitro and in-vivo activity was demonstrated with various cell-penetrating octaarginine salts of fosmidomycin: intravenous injection to mice caused exitus of the animals within minutes, even at doses as low as 1.4 μmol/kg (Table 2). The results show that use of CPPs for drug delivery, for instance to cancer cells and tissues, must be considered with due care. The biopolymer cyanophycin is a poly-aspartic acid containing argininylated side chains (Figure 4); its building block is the dipeptide H-βAsp-αArg-OH (H-Adp-OH). To test and compare the biological properties with those of octaarginines we synthesized Adp8-derivatives (Figure 5). Intravenouse injection of H-Adp8-NH2 into the tail vein of mice with doses as high as 45 μmol/kg causes no symptoms whatsoever (Table 3), but H-Adp8-NH2 is not cell penetrating (HEK293 and MCF-7 cells, Figure 6). On the other hand, the fluorescently labeled octamers FAM-(Adp(OMe))8-NH2 and FAM-(Adp(NMe2))8-NH2 with ester and amide groups in the side chains exhibit mediocre to high cell-wall permeability (Figure 6), and are toxic (Table 3). Possible reasons for this behavior are discussed (Figure 7) and corresponding NMR spectra are presented (Figure 8).
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Affiliation(s)
- Marcel Grogg
- Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Vladimir-Prelog-Weg 3, CH-8093 Zürich, Switzerland
| | - Donald Hilvert
- Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Vladimir-Prelog-Weg 3, CH-8093 Zürich, Switzerland
| | - Marc-Olivier Ebert
- Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Vladimir-Prelog-Weg 3, CH-8093 Zürich, Switzerland
| | - Albert K Beck
- Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Vladimir-Prelog-Weg 3, CH-8093 Zürich, Switzerland
| | - Dieter Seebach
- Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Vladimir-Prelog-Weg 3, CH-8093 Zürich, Switzerland
| | - Felix Kurth
- Department of Biosystems Science and Engineering, ETH Zürich, BSD H 368, Mattenstrasse 26, CH-4058 Basel, Switzerland
| | - Petra S Dittrich
- Department of Biosystems Science and Engineering, ETH Zürich, BSD H 368, Mattenstrasse 26, CH-4058 Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, CH-4056 Basel, Switzerland
| | - Sergio Wittlin
- Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4051 Basel, Switzerland
| | - Matthias Rottmann
- Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4051 Basel, Switzerland
| | - Pascal Mäser
- Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4051 Basel, Switzerland
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Fischer C, Sparr C. Synthesis of 1,5-bifunctional organolithium reagents by a double directed ortho-metalation: Direct transformation of esters into 1,8-dimethoxy-acridinium salts. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.04.060] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Arylated heterocyclic fluorophores are particularly useful scaffolds for numerous applications, such as bioimaging or synthetic photochemistry. While variation of the substitution pattern at the heterocycle and aryl groups allows dye modulation, the bond rotational barriers are also strongly affected. Unsymmetrically substituted ring systems of rotationally restricted arylated heterocycles therefore lead to configurationally stable atropisomeric fluorophores. Herein, we describe these characteristics by determining the properties and configurational stability of atropisomeric, tri-ortho-substituted naphthyl-acridinium fluorophores. A significant barrier to rotation of >120 kJ mol–1 was measured, which renders these dyes and related compounds distinct atropisomers with stereoisomer-specific properties over a broad temperature range.
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Lotter D, Castrogiovanni A, Neuburger M, Sparr C. Catalyst-Controlled Stereodivergent Synthesis of Atropisomeric Multiaxis Systems. ACS Cent Sci 2018; 4:656-660. [PMID: 29806013 PMCID: PMC5968508 DOI: 10.1021/acscentsci.8b00204] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Indexed: 06/08/2023]
Abstract
Molecular scaffolds with multiple rotationally restricted bonds allow a precise spatial positioning of functional groups. However, their synthesis requires methods addressing the configuration of each stereogenic axis. We report here a catalyst-stereocontrolled synthesis of atropisomeric multiaxis systems enabling divergence from the prevailing stereochemical reaction path. By using ion-pairing catalysts in arene-forming aldol condensations, a strong substrate-induced stereopreference can be overcome to provide structurally well-defined helical oligo-1,2-naphthylenes. The configuration of up to four stereogenic axes was individually catalyst-controlled, affording quinquenaphthalenes with a unique topology.
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Affiliation(s)
- Dominik Lotter
- Department of Chemistry, University
of Basel, St. Johanns-Ring
19, 4056 Basel, Switzerland
| | | | - Markus Neuburger
- Department of Chemistry, University
of Basel, St. Johanns-Ring
19, 4056 Basel, Switzerland
| | - Christof Sparr
- Department of Chemistry, University
of Basel, St. Johanns-Ring
19, 4056 Basel, Switzerland
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Link A, Sparr C. Remote Central-to-Axial Chirality Conversion: Direct Atroposelective Ester to Biaryl Transformation. Angew Chem Int Ed Engl 2018; 57:7136-7139. [DOI: 10.1002/anie.201803472] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Achim Link
- Department of Chemistry; University of Basel; St. Johanns-Ring 19 4056 Basel Switzerland
| | - Christof Sparr
- Department of Chemistry; University of Basel; St. Johanns-Ring 19 4056 Basel Switzerland
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