1
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Kulsha AV, Ivashkevich OA. pH Indicators for Strong Molecular Bases: A Theoretical Approach. J Phys Chem A 2024. [PMID: 38817074 DOI: 10.1021/acs.jpca.4c02567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
The transition points in hexamethylphosphoramide are theoretically studied for a series of acid-base indicators. Three new indicators with multiple transition points and deeply colored low-nucleophilic anions are designed. A general basicity scale is established for highly basic hexamethylphosphoramide solutions, expanding beyond the basicity of the strongest currently known molecular bases.
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Affiliation(s)
- Andrey V Kulsha
- Belarusian State University, 4 Nezavisimosti Avenue, Minsk 220030, Republic of Belarus
| | - Oleg A Ivashkevich
- Research Institute for Physical Chemical Problems of the Belarusian State Unversity, 14 Leningradskaya str., Minsk 220006, Republic of Belarus
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2
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Capocasa G, Frateloreto F, Valentini M, Di Stefano S. Molecular entanglement can strongly increase basicity. Commun Chem 2024; 7:116. [PMID: 38806668 PMCID: PMC11133330 DOI: 10.1038/s42004-024-01205-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 05/17/2024] [Indexed: 05/30/2024] Open
Abstract
Brønsted basicity is a fundamental chemical property featured by several kinds of inorganic and organic compounds. In this Review, we treat a particularly high basicity resulting from the mechanical entanglement involving two or more molecular subunits in catenanes and rotaxanes. Such entanglement allows a number of basic sites to be in close proximity with each other, highly increasing the proton affinity in comparison with the corresponding, non-entangled counterparts up to obtain superbases, properly defined as mechanically interlocked superbases. In the following pages, the development of this kind of superbases will be described with a historical perusal, starting from the initial, serendipitous findings up to the most recent reports where the strong basic property of entangled molecular units is the object of a rational design.
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Affiliation(s)
- Giorgio Capocasa
- Department of Chemistry Università di Roma La Sapienza and ISB-CNR Sede Secondaria di Roma - Meccanismi di Reazione P.le A. Moro 5, I-00185, Roma, Italy
| | - Federico Frateloreto
- Department of Chemistry Università di Roma La Sapienza and ISB-CNR Sede Secondaria di Roma - Meccanismi di Reazione P.le A. Moro 5, I-00185, Roma, Italy
| | - Matteo Valentini
- Department of Chemistry Università di Roma La Sapienza and ISB-CNR Sede Secondaria di Roma - Meccanismi di Reazione P.le A. Moro 5, I-00185, Roma, Italy
| | - Stefano Di Stefano
- Department of Chemistry Università di Roma La Sapienza and ISB-CNR Sede Secondaria di Roma - Meccanismi di Reazione P.le A. Moro 5, I-00185, Roma, Italy.
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3
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Tampellini N, Mercado BQ, Miller SJ. Scaffold-Oriented Asymmetric Catalysis: Conformational Modulation of Transition State Multivalency during a Catalyst-Controlled Assembly of a Pharmaceutically Relevant Atropisomer. Chemistry 2024; 30:e202401109. [PMID: 38507249 PMCID: PMC11132932 DOI: 10.1002/chem.202401109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 03/20/2024] [Indexed: 03/22/2024]
Abstract
A new class of superbasic, bifunctional peptidyl guanidine catalysts is presented, which enables the organocatalytic, atroposelective synthesis of axially chiral quinazolinediones. Computational modeling unveiled the conformational modulation of the catalyst by a novel phenyl urea N-cap, that preorganizes the structure into the active, folded state. A previously unanticipated noncovalent interaction involving a difluoroacetamide acting as a hybrid mono- or bidentate hydrogen bond donor emerged as a decisive control element inducing atroposelectivity. These discoveries spurred from a scaffold-oriented project inspired from a fascinating investigational BTK inhibitor featuring two stable chiral axes and relies on a mechanistic framework that was foreign to the extant lexicon of asymmetric catalysis.
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Affiliation(s)
- Nicolò Tampellini
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06511 (USA)
| | - Brandon Q. Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06511 (USA)
| | - Scott J. Miller
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06511 (USA)
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4
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Yang X, Gao H, Yan J, Zhou J, Shi L. Intramolecular chaperone-assisted dual-anchoring activation (ICDA): a suitable preorganization for electrophilic halocyclization. Chem Sci 2024; 15:6130-6140. [PMID: 38665529 PMCID: PMC11041335 DOI: 10.1039/d4sc00581c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 03/20/2024] [Indexed: 04/28/2024] Open
Abstract
The halocyclization reaction represents one of the most common methodologies for the synthesis of heterocyclic molecules. Many efforts have been made to balance the relationship between structure, reactivity and selectivity, including the design of new electrophilic halogenation reagents and the utilization of activating strategies. However, discovering universal reagents or activating strategies for electrophilic halocyclization remains challenging due to the case-by-case practice for different substrates or different cyclization models. Here we report an intramolecular chaperone-assisted dual-anchoring activation (ICDA) model for electrophilic halocyclization, taking advantage of the non-covalent dual-anchoring orientation as the driving force. This protocol allows a practical, catalyst-free and rapid approach to access seven types of small-sized, medium-sized, and large-sized heterocyclic units and to realize polyene-like domino halocyclizations, as exemplified by nearly 90 examples, including a risk-reducing flow protocol for gram-scale synthesis. DFT studies verify the crucial role of ICDA in affording a suitable preorganization for transition state stabilization and X+ transfer acceleration. The utilization of the ICDA model allows a spatiotemporal adjustment to straightforwardly obtain fast, selective and high-yielding synthetic transformations.
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Affiliation(s)
- Xihui Yang
- School of Science (Shenzhen), School of Chemistry and Chemical Engineering, Harbin Institute of Technology Shenzhen 518055 China
| | - Haowei Gao
- School of Science (Shenzhen), School of Chemistry and Chemical Engineering, Harbin Institute of Technology Shenzhen 518055 China
| | - Jiale Yan
- School of Science (Shenzhen), School of Chemistry and Chemical Engineering, Harbin Institute of Technology Shenzhen 518055 China
| | - Jia Zhou
- School of Science (Shenzhen), School of Chemistry and Chemical Engineering, Harbin Institute of Technology Shenzhen 518055 China
- Laboratory of Urban Water Resources and Environment, Harbin Institute of Technology (Shenzhen) Shenzhen 518055 China
| | - Lei Shi
- School of Science (Shenzhen), School of Chemistry and Chemical Engineering, Harbin Institute of Technology Shenzhen 518055 China
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5
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Zhou L, Reilly LT, Shi C, Quinn EC, Chen EYX. Proton-triggered topological transformation in superbase-mediated selective polymerization enables access to ultrahigh-molar-mass cyclic polymers. Nat Chem 2024:10.1038/s41557-024-01511-2. [PMID: 38649467 DOI: 10.1038/s41557-024-01511-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 03/18/2024] [Indexed: 04/25/2024]
Abstract
The selective synthesis of ultrahigh-molar-mass (UHMM, >2 million Da) cyclic polymers is challenging as an exceptional degree of spatiotemporal control is required to overcome the possible undesired reactions that can compete with the desired intramolecular cyclization. Here we present a counterintuitive synthetic methodology for cyclic polymers, represented here by polythioesters, which proceeds via superbase-mediated ring-opening polymerization of gem-dimethylated thiopropiolactone, followed by macromolecular cyclization triggered by protic quenching. This proton-triggered linear-to-cyclic topological transformation enables selective, linear polymer-like access to desired cyclic polythioesters, including those with UHMM surpassing 2 MDa. In addition, this method eliminates the need for stringent conditions such as high dilution to prevent or suppress linear polymer contaminants and presents the opposite scenario in which protic-free conditions are required to prevent cyclic polymer formation, which is capitalized to produce cyclic polymers on demand. Furthermore, such UHMM cyclic polythioester exhibits not only much enhanced thermostability and mechanical toughness, but it can also be quantitatively recycled back to monomer under mild conditions due to its gem-disubstitution.
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Affiliation(s)
- Li Zhou
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Liam T Reilly
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Changxia Shi
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Ethan C Quinn
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Eugene Y-X Chen
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA.
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6
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Kikkawa S, Fujiki Y, Chudatemiya V, Nagakari H, Shibusawa K, Hirayama J, Nakatani N, Yamazoe S. Water-Tolerant Superbase Polyoxometalate [H 2(Nb 6O 19)] 6- for Homogeneous Catalysis. Angew Chem Int Ed Engl 2024; 63:e202401526. [PMID: 38388816 DOI: 10.1002/anie.202401526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 02/20/2024] [Accepted: 02/21/2024] [Indexed: 02/24/2024]
Abstract
Here, doubly protonated Lindqvist-type niobium oxide cluster [H2(Nb6O19)]6-, fabricated by microwave-assisted hydrothermal synthesis, exhibited superbase catalysis for Knoevenagel and crossed aldol condensation reactions accompanied by activating C-H bond with pKa >26 and proton abstraction from a base indicator with pKa=26.5. Surprisingly, [H2(Nb6O19)]6- exhibited water-tolerant superbase properties for Knoevenagel and crossed aldol condensation reactions in the presence of water, although it is well known that the strong basicity of metal oxides and organic superbase is typically lost by the adsorption of water. Density functional theory calculation revealed that the basic surface oxygens that share the corner of NbO6 units in [H2(Nb6O19)]8- maintained the negative charges even after proton adsorption. This proton capacity and the presence of un-protonated basic sites led to the water tolerance of the superbase catalysis.
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Affiliation(s)
- Soichi Kikkawa
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
- Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30, Goryo-Ohara, Nishikyo-ku, Kyoto, 615-8245, Japan
| | - Yu Fujiki
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Vorakit Chudatemiya
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Hiroki Nagakari
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Kazuki Shibusawa
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Jun Hirayama
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
- Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30, Goryo-Ohara, Nishikyo-ku, Kyoto, 615-8245, Japan
| | - Naoki Nakatani
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Seiji Yamazoe
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo, 192-0397, Japan
- Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University, 1-30, Goryo-Ohara, Nishikyo-ku, Kyoto, 615-8245, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) 4-1-8, Honcho, Kawaguchi, Saitama, 332-0012, Japan
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7
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Affiliation(s)
- Martin A L Johansen
- Department of Chemistry and Center for Sustainable STEM Education, UiT The Arctic University of Norway, Tromsø, Norway
| | - Abhik Ghosh
- Department of Chemistry and Center for Sustainable STEM Education, UiT The Arctic University of Norway, Tromsø, Norway.
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8
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Mechanistic DFT Study of 1,3-Dipolar Cycloadditions of Azides with Guanidine. Molecules 2023; 28:molecules28052342. [PMID: 36903588 PMCID: PMC10004754 DOI: 10.3390/molecules28052342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 02/22/2023] [Accepted: 02/28/2023] [Indexed: 03/06/2023] Open
Abstract
Density functional calculations SMD(chloroform)//B3LYP/6-311+G(2d,p) were employed in the computational study of 1,3-dipolar cycloadditions of azides with guanidine. The formation of two regioisomeric tetrazoles and their rearrangement to cyclic aziridines and open-chain guanidine products were modeled. The results suggest the feasibility of an uncatalyzed reaction under very drastic conditions since the thermodynamically preferred reaction path (a), which involves cycloaddition by binding the carbon atom from guanidine to the terminal azide nitrogen atom, and the guanidine imino nitrogen with the inner N atom from the azide, has an energy barrier higher than 50 kcal mol-1. The formation of the other regioisomeric tetrazole (imino nitrogen interacts with terminal N atom of azide) in direction (b) can be more favorable and proceed under milder conditions if alternative activation of the nitrogen molecule releases (e.g., photochemical activation), or deamination could be achieved because these processes have the highest barrier in the less favorable (b) branch of the mechanism. The introduction of substituents should favorably affect the cycloaddition reactivity of the azides, with the greatest effects expected for the benzyl and perfluorophenyl groups.
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9
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Glasovac Z, Barešić L, Margetić D. A DFT Investigation of the Reactivity of Guanidinium Salts in Tandem aza-Michael Addition/Intramolecular Cyclization. Molecules 2023; 28:molecules28052218. [PMID: 36903463 PMCID: PMC10005421 DOI: 10.3390/molecules28052218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 02/22/2023] [Accepted: 02/24/2023] [Indexed: 03/06/2023] Open
Abstract
A proposed mechanism of the reaction of guanidinium chlorides with dimethyl acetylenedicarboxylate in a tandem aza-Michael addition reaction/intramolecular cyclization was investigated by DFT M06-2X and B3LYP computational approaches. The energies of the products were compared against the G3, M08-HX, M11, and wB97xD data or experimentally obtained product ratios. The structural diversity of the products was interpreted by the concurrent formation of different tautomers formed in situ upon deprotonation with a 2-chlorofumarate anion. A comparison of relative energies of the characteristic stationary points along the examined reaction paths indicated that the initial nucleophilic addition is energetically the most demanding process. The overall reaction is strongly exergonic, as predicted by both methods, which is primarily due to methanol elimination during the intramolecular cyclization step producing cyclic amide structures. Formation of a five-membered ring upon intramolecular cyclization is highly favored for the acyclic guanidine, while optimal product structure for the cyclic guanidines is based on a 1,5,7-triaza [4.3.0]-bicyclononane skeleton. Relative stabilities of the possible products calculated by the employed DFT methods were compared against the experimental product ratio. The best agreement was obtained for the M08-HX approach while the B3LYP approach provided somewhat better results than the M06-2X and M11 methods.
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10
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Valadbeigi Y, Taheri R. Superbasicity of imines with bicyclo[5.1.0]octa-1,3,5,7-tetraene scaffold due to electron delocalization in the conjugated acids. COMPUT THEOR CHEM 2023. [DOI: 10.1016/j.comptc.2023.114076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
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11
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Khazali M, Rouhani M, Saeidian H. Utilizing the synergistic effect between imidazole aromaticity and guanidine structure for the computational design of novel uncharged organic superbases. J Mol Struct 2023. [DOI: 10.1016/j.molstruc.2022.134348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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12
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N,N'-Di-Boc-2H-Isoindole-2-carboxamidine-First Guanidine-Substituted Isoindole. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27248954. [PMID: 36558087 PMCID: PMC9781607 DOI: 10.3390/molecules27248954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/10/2022] [Accepted: 12/11/2022] [Indexed: 12/23/2022]
Abstract
Synthesis of N,N'-Di-Boc-2H-isoindole-2-carboxamidine, the first representative of isoindoles containing guanidine functionality, was carried out. The cycloaddition reactivity of this new Diels-Alder heterodiene was studied and the title compound was employed as a cycloaddition delivery reagent for guanidine functionality. Higher reactivity was found in comparison with the corresponding pyrrole derivative. Substitution with fluorine or guanidine functionality does not change the reactivities of isoindoles, and these findings are in good accord with computational results.
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13
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Ghosh A, Conradie J. Theoretical Photoelectron Spectroscopy of Low-Valent Carbon Species: A ∼6 eV Range of Ionization Potentials among Carbenes, Ylides, and Carbodiphosphoranes. ACS ORGANIC & INORGANIC AU 2022; 3:92-95. [PMID: 37035281 PMCID: PMC10080723 DOI: 10.1021/acsorginorgau.2c00045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 11/09/2022] [Accepted: 11/11/2022] [Indexed: 12/04/2022]
Abstract
High-quality density functional theory calculations underscore a nearly 6 eV range for the ionization potentials (IPs) of neutral, low-valent carbon compounds, including carbenes, ylides, and zero-valent carbon compounds (carbones) such as carbodiphosphoranes (CDPs) and carbodicarbenes. Thus, adiabatic IPs as low as 5.5 ± 0.1 eV are predicted for CDPs, which are about 0.7-1.2 eV lower than those of simple phosphorus and sulfur ylides. In contrast, the corresponding values for N-heterocyclic carbenes are about 8.0 eV while those for simple singlet carbenes such as dichlorocarbene and difluorocarbene range from about 9.0 eV to well over 11.0 eV.
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Affiliation(s)
- Abhik Ghosh
- Department of Chemistry, University of Tromsø, Tromsø N-9037, Norway
| | - Jeanet Conradie
- Department of Chemistry, University of Tromsø, Tromsø N-9037, Norway
- Department of Chemistry, University of the Free State, Bloemfontein 9300, Republic of South Africa
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14
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Fritz-Langhals E. Unique Superbase TBD (1,5,7-Triazabicyclo[4.4.0]dec-5-ene): From Catalytic Activity and One-Pot Synthesis to Broader Application in Industrial Chemistry. Org Process Res Dev 2022. [DOI: 10.1021/acs.oprd.2c00248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elke Fritz-Langhals
- Department of Chemistry, Technical University of Munich (TUM), Lichtenbergstraße 4, D-85747 Garching, Germany
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15
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Lops C, Pengo P, Pasquato L. Highly Efficient Darzens Reactions Mediated by Phosphazene Bases under Mild Conditions. Chemistry 2022; 11:e202200179. [PMID: 36207800 PMCID: PMC9547082 DOI: 10.1002/open.202200179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 08/30/2022] [Indexed: 11/18/2022]
Abstract
The highly basic and poorly nucleophilic phosphazene base P1‐t‐Bu promotes the Darzens condensation of α‐halo esters with aromatic aldehydes affording α,β‐epoxy esters in nearly quantitative yields under mild conditions and in short reaction times. The more basic P4‐t‐Bu phosphazene was found useful with low reactivity aldehydes. These reactions can be performed in aprotic organic solvents of low polarity, thus minimizing the hydrolysis of α,β‐epoxy esters which often accompanies the base‐promoted Darzens condensations.
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Affiliation(s)
- Carmine Lops
- Department of Chemical and Pharmaceutical SciencesUniversity of TriesteVia L. Giorgieri 134127TriesteItaly,Aptuit – an Evotec CompanyVia A. Fleming 437135VeronaItaly
| | - Paolo Pengo
- Department of Chemical and Pharmaceutical SciencesUniversity of TriesteVia L. Giorgieri 134127TriesteItaly
| | - Lucia Pasquato
- Department of Chemical and Pharmaceutical SciencesUniversity of TriesteVia L. Giorgieri 134127TriesteItaly
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16
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Affiliation(s)
- Son H. Doan
- School of Chemistry, University of New South Wales, Sydney 2052, New South Wales, Australia
| | - Nhan N. H. Ton
- School of Chemistry, University of New South Wales, Sydney 2052, New South Wales, Australia
| | - Binh Khanh Mai
- Department of Chemistry, University of Pittsburgh, Pittsburgh 15260, Pennsylvania, United States
| | - Thanh Vinh Nguyen
- School of Chemistry, University of New South Wales, Sydney 2052, New South Wales, Australia
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17
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Modeling pKa of the Brønsted Bases as an Approach to the Gibbs Energy of the Proton in Acetonitrile. Int J Mol Sci 2022; 23:ijms231810576. [PMID: 36142490 PMCID: PMC9502073 DOI: 10.3390/ijms231810576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 11/17/2022] Open
Abstract
A simple but efficient computational approach to calculate pKa in acetonitrile for a set of phosphorus, nitrogen, and carbon bases was established. A linear function that describes relations between the calculated ΔG’a.sol(BH+) and pKa values was determined for each group of bases. The best model was obtained through the variations in the basis set, in the level of theory (density functionals or MP2), and in the continuum solvation model (IPCM, CPCM, or SMD). The combination of the IPCM/B3LYP/6-311+G(d,p) solvation approach with MP2/6-311+G(2df,p)//B3LYP/6-31G(d) gas-phase energies provided very good results for all three groups of bases with R2 values close to or above 0.99. Interestingly, the slopes and the intercepts of the obtained linear functions showed significant deviations from the theoretical values. We made a linear plot utilizing all the conducted calculations and all the structural variations and employed methods to prove the systematic nature of the intercept/slope dependence. The interpolation of the intercept to the ideal slope value enabled us to determine the Gibbs energy of the proton in acetonitrile, which amounted to −258.8 kcal mol−1. The obtained value was in excellent agreement with previously published results.
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18
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Deljuie F, Rouhani M, Saeidian H. Exceptional design of super/hyperbases based on spiro‐alleneic structures in gas phase: A DFT study. J PHYS ORG CHEM 2022. [DOI: 10.1002/poc.4423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Fatemeh Deljuie
- Department of Chemistry, Science and Research Branch Islamic Azad University Tehran Iran
| | - Morteza Rouhani
- Department of Chemistry, Science and Research Branch Islamic Azad University Tehran Iran
| | - Hamid Saeidian
- Department of Science Payame Noor University (PNU) Tehran Iran
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19
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Pyridoneimine-catalyzed anomeric aqueous oxa-Michael additions of native mono- and disaccharides. Carbohydr Res 2022; 520:108610. [PMID: 35863121 DOI: 10.1016/j.carres.2022.108610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 06/03/2022] [Accepted: 06/06/2022] [Indexed: 11/23/2022]
Abstract
A pyridoneimine-catalyzed oxa-Michael addition of protecting groups-free, native mono- and disaccharides with Michael acceptors in aq. solution is reported. Several mono- and disaccharides are reacted with acceptors, namely, methylvinyl ketone, acrylonitrile and tert-butyl acrylate in aq. solution, the addition catalyzed by n-pentylpyridone imine. The addition occurs site-selectively at the anomeric lactol and the remaining hydroxy functionalities are un-affected. The resulting keto-glycopyranoside products are explored in aldol, allylation and oxime product formation, occurring at either α-methyl moiety or at the keto-moiety, with appropriate synthons. In another direction, the keto-glycopyranoside is functionalized further with amino acids through reductive amination in aq. methanol solution. Formation of hemiacetal anion occurs in the presence of pyridoneimine in aq. Solution, enabling subsequent addition to occur with acceptors. Facile reductive amination of the resulting keto-glycoside provides an avenue for conjugations with amino acids in the present work.
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20
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Raczyńska ED, Gal JF, Maria PC, Sakhawat GS, Fahim MQ, Saeidian H. Nitriles with High Gas-Phase Basicity-Part II Transmission of the Push-Pull Effect through Methylenecyclopropene and Cyclopropenimine Scaffolds Intercalated between Different Electron Donor(s) and the Cyano N-Protonation Site. Molecules 2022; 27:4370. [PMID: 35889241 PMCID: PMC9323925 DOI: 10.3390/molecules27144370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 07/02/2022] [Accepted: 07/04/2022] [Indexed: 11/16/2022] Open
Abstract
This work extends our earlier quantum chemical studies on the gas-phase basicity of very strong N-bases to two series of nitriles containing the methylenecyclopropene and cyclopropenimine scaffolds with dissymmetrical substitution by one or two electron-donating substituents such as Me, NR2, N=C (NR2)2, and N=P (NR2)3, the last three being strong donors. For a proper prediction of their gas-phase base properties, all potential isomeric phenomena and reasonable potential protonation sites are considered to avoid possible inconsistencies when evaluating the energetic parameters and associated protonation or deprotonation equilibria B + H+ = BH+. More than 250 new isomeric structures for neutral and protonated forms are analyzed. The stable structures are selected and the favored ones identified. The microscopic (kinetic) gas-phase basicity parameters (PA and GB) corresponding to N sites (cyano and imino in the cyclopropenimine or in the substituents) in each isomer are calculated. The macroscopic (thermodynamic) PAs and GBs, referring to the isomeric mixtures of favored isomers, are also estimated. The total (pushing) substituent effects are analyzed for monosubstituted and disubstituted derivatives containing two identical or two different substituents. Electron delocalization is examined in the two π-π conjugated transmitters, the methylenecyclopropene and cyclopropenimine scaffolds. The aromatic character of the three-membered ring is also discussed.
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Affiliation(s)
- Ewa D. Raczyńska
- Department of Chemistry, Warsaw University of Life Sciences (SGGW), 02-776 Warsaw, Poland
| | - Jean-François Gal
- Institut de Chimie de Nice, Université Côte d’Azur, Parc Valrose, 06108 Nice, France;
| | - Pierre-Charles Maria
- Institut de Chimie de Nice, Université Côte d’Azur, Parc Valrose, 06108 Nice, France;
| | - Ghulam Sakhi Sakhawat
- Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran P.O. Box 14515-775, Iran; (G.S.S.); (M.Q.F.)
| | - Mohammad Qasem Fahim
- Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran P.O. Box 14515-775, Iran; (G.S.S.); (M.Q.F.)
| | - Hamid Saeidian
- Department of Science, Payame Noor University (PNU), Tehran P.O. Box 19395-4697, Iran
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21
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Kulsha AV, Ragoyja EG, Ivashkevich OA. Strong Bases Design: Predicted Limits of Basicity. J Phys Chem A 2022; 126:3642-3652. [PMID: 35657384 DOI: 10.1021/acs.jpca.2c00521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Brønsted superbases have wide applications in organic chemistry due to their ability to activate C-H bonds. The strongest neutral bases to date are substituted aminophosphazenes developed in the late 1980s by Reinhard Schwesinger. Since then, much effort has been expended to create even stronger neutral bases. In this article, the reasons for the instability of very basic compounds are investigated by means of high-level quantum-chemical calculations. Theoretical basicity limits are suggested for solutions as well as for the gas phase. A record-breaking superbase most likely to be synthesizable and stable at ambient conditions is proposed. Hexamethylphosphoramide is considered a reliable ionizing solvent for superbases.
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Affiliation(s)
- Andrey V Kulsha
- Chemical Department, Belarusian State University, 4 Nezavisimosti Avenue, 220030 Minsk, Republic of Belarus
| | - Ekaterina G Ragoyja
- Chemical Department, Belarusian State University, 4 Nezavisimosti Avenue, 220030 Minsk, Republic of Belarus
| | - Oleg A Ivashkevich
- Laboratory for Chemistry of Condensed Systems, Research Institute for Physical Chemical Problems of the Belarusian State University, 14 Leningradskaya Street, 220006 Minsk, Republic of Belarus
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22
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Luo C, Alegre-Requena JV, Sujansky SJ, Pajk SP, Gallegos LC, Paton RS, Bandar JS. Mechanistic Studies Yield Improved Protocols for Base-Catalyzed Anti-Markovnikov Alcohol Addition Reactions. J Am Chem Soc 2022; 144:9586-9596. [PMID: 35605253 DOI: 10.1021/jacs.1c13397] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The catalytic anti-Markovnikov addition of alcohols to simple alkenes is a longstanding synthetic challenge. We recently disclosed the use of organic superbase catalysis for the nucleophilic addition of alcohols to activated styrene derivatives. This article describes mechanistic studies on this reversible reaction, including thermodynamic and kinetic profiling as well as computational modeling. Our findings show the negative entropy of addition is counterbalanced by an enthalpy that is most favored in nonpolar solvents. However, a large negative alcohol rate order under these conditions indicates excess alcohol sequesters the active alkoxide ion pairs, slowing the reaction rate. These observations led to an unexpected solution to a thermodynamically challenging reaction: use of less alcohol enables faster addition, which in turn allows for lower reaction temperatures to counteract Le Chatelier's principle. Thus, our original method has been improved with new protocols that do not require excess alcohol stoichiometry, enable an expanded alkene substrate scope, and allow for the use of more practical catalyst systems. The generality of this insight for other challenging hydroetherification reactions is also demonstrated through new alkenol cyclization and oxa-Michael addition reactions.
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Affiliation(s)
- Chaosheng Luo
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Juan V Alegre-Requena
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Stephen J Sujansky
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Spencer P Pajk
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Liliana C Gallegos
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Robert S Paton
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Jeffrey S Bandar
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
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23
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Bai YJ, Cheng ML, Zheng XH, Zhang SY, Wang PA. Chiral Cyclopropenimine-catalyzed Asymmetric Michael Addition of Bulky Glycine Imine to α,β-Unsaturated Isoxazoles. Chem Asian J 2022; 17:e202200131. [PMID: 35415949 DOI: 10.1002/asia.202200131] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/26/2022] [Indexed: 11/11/2022]
Abstract
A highly efficient asymmetric Michael addition of bulky glycine imine to α,β-unsaturated isoxazoles has been achieved by using 5 mol% of chiral cyclopropenimine as a chiral organo-superbase catalyst under mild conditions. Michael adducts were obtained in excellent yields (up to 97%) and stereoselectivities (up to>99 : 1 dr and 98% ee). A significant solvent effect was found in these chiral organosuperbase catalyzed asymmetric Michael reactions. Gram-scale preparation of Michael adducts and their transformations are realized to provide corresponding products without loss of stereoselectivities. The configurations of Michael adduct was determined by single-crystal X-ray diffraction analysis.
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Affiliation(s)
- Yu-Jun Bai
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, The College of Life Sciences, Northwest University, Xi'an, 710069, P. R. China) E-mails.,Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
| | - Mei-Ling Cheng
- Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
| | - Xiao-Hui Zheng
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, The College of Life Sciences, Northwest University, Xi'an, 710069, P. R. China) E-mails
| | - Sheng-Yong Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, The College of Life Sciences, Northwest University, Xi'an, 710069, P. R. China) E-mails.,Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
| | - Ping-An Wang
- Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
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24
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Dey K, Jayaraman N. Anomeric alkylations and acylations of unprotected mono- and disaccharides mediated by pyridoneimine in aqueous solutions. Chem Commun (Camb) 2022; 58:2224-2227. [PMID: 35072677 DOI: 10.1039/d1cc07056h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A site-specific deprotonation followed by alkylations and acylations of sugar hemiacetals to the corresponding alkyl glycosides and acylated sugars in aqueous solutions is disclosed herein. Pyridoneimine as a new base is developed to mediate the deprotonation of readily available sugar hemiacetals and further reactions with alkylation and acylation agents.
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Affiliation(s)
- Kalyan Dey
- Indian Institute of Science, Bangalore 560012, India.
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25
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Saha A, Ganguly B. The design of C2-chiral bases with dual basic sites predicted to exceed the range of superbasicity: a computational study. NEW J CHEM 2022. [DOI: 10.1039/d2nj03537e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A set of C2-chiral bases with bis-protonation sites (1–9) on dimethyl-binaphthalene derivatives have been explored using the B3LYP/6-311+G(d,p) level and the proton affinities calculated are in the range of superbases for both the sites.
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Affiliation(s)
- Anusuya Saha
- Computation and Simulation Unit, Analytical and Environmental Science Division and Centralized Instrument Facility, CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat-364002, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Bishwajit Ganguly
- Computation and Simulation Unit, Analytical and Environmental Science Division and Centralized Instrument Facility, CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat-364002, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
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