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Sreedharan R, Gandhi T. Masters of Mediation: MN(SiMe 3) 2 in Functionalization of C(sp 3)-H Latent Nucleophiles. Chemistry 2024; 30:e202400435. [PMID: 38497321 DOI: 10.1002/chem.202400435] [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: 01/31/2024] [Revised: 03/16/2024] [Accepted: 03/18/2024] [Indexed: 03/19/2024]
Abstract
Organoalkali compounds have undergone a far-reaching transformation being a coupling partner to a mediator in unusual organic conversions which finds its spot in the field of sustainable synthesis. Transition-metal catalysis has always been the priority in C(sp3)-H bond functionalization, however alternatively, in recent times this has been seriously challenged by earth-abundant alkali metals and their complexes arriving at new sustainable organometallic reagents. In this line, the importance of MN(SiMe3)2 (M=Li, Na, K & Cs) reagent revived in C(sp3)-H bond functionalization over recent years in organic synthesis is showcased in this minireview. MN(SiMe3)2 reagent with higher reactivity, enhanced stability, and bespoke cation-π interaction have shown eye-opening mediated processes such as C(sp3)-C(sp3) cross-coupling, radical-radical cross-coupling, aminobenzylation, annulation, aroylation, and other transformations to utilize readily available petrochemical feedstocks. This article also emphasizes the unusual reactivity of MN(SiMe3)2 reagent in unreactive and robust C-X (X=O, N, F, C) bond cleavage reactions that occurred alongside the C(sp3)-H bond functionalization. Overall, this review encourages the community to exploit the untapped potential of MN(SiMe3)2 reagent and also inspires them to take up this subject to even greater heights.
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Affiliation(s)
- Ramdas Sreedharan
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India
| | - Thirumanavelan Gandhi
- Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore, 632014, Tamil Nadu, India
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2
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Schmitt HL, Martymianov D, Green O, Delcaillau T, Park Kim YS, Morandi B. Regiodivergent Ring-Expansion of Oxindoles to Quinolinones. J Am Chem Soc 2024; 146:4301-4308. [PMID: 38335924 PMCID: PMC10885155 DOI: 10.1021/jacs.3c12119] [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: 02/12/2024]
Abstract
The development of divergent methods to expedite structure-activity relationship studies is crucial to streamline discovery processes. We developed a rare example of regiodivergent ring expansion to access two regioisomers from a common starting material. To enable this regiodivergence, we identified two distinct reaction conditions for transforming oxindoles into quinolinone isomers. The presented methods proved to be compatible with a variety of functional groups, which enabled the late-stage diversification of bioactive oxindoles as well as facilitated the synthesis of quinolinone drugs and their derivatives.
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Affiliation(s)
- Hendrik L Schmitt
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich, Switzerland
| | - Den Martymianov
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich, Switzerland
| | - Ori Green
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich, Switzerland
| | - Tristan Delcaillau
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich, Switzerland
| | - Young Seo Park Kim
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich, Switzerland
| | - Bill Morandi
- Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich, Switzerland
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3
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You Q, Collum DB. Carbon-Nitrogen Bond Formation Using Sodium Hexamethyldisilazide: Solvent-Dependent Reactivities and Mechanisms. J Am Chem Soc 2023; 145:23568-23584. [PMID: 37857357 DOI: 10.1021/jacs.3c07317] [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: 10/21/2023]
Abstract
The solvent-dependent reactivity of sodium hexamethyldisilazide (NaHMDS) toward carbon-centered electrophiles reveals reactions that are poorly represented or unrepresented in the literature, including direct aminolysis of aromatic methyl esters to give carboxamides, nitriles, or amidines, depending on the choice of solvent. SNAr substitutions of aryl halides and opening of terminal epoxides are also examined. A combination of 1H and 29Si nuclear magnetic resonance (NMR) spectroscopic studies using [15N]NaHMDS, kinetic studies, and computational studies reveals the complex mechanistic basis of the preferences for simple aryl carboxamides in toluene and dimethylethylamine and arylnitriles or amidines in tetrahydrofuran (THF). A prevalence of dimer- and mixed dimer-based chemistry even starting from the observable NaHMDS monomer in THF solution is notable.
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Affiliation(s)
- Qiulin You
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
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4
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Boyarskaya DV, Ongaro A, Piemontesi C, Wang Q, Zhu J. Synthesis of 3-Acyloxyindolenines by TiCl 3-Mediated Reductive Cyclization of 2-( ortho-Nitroaryl)-Substituted Enol Esters. Org Lett 2022; 24:7004-7008. [PMID: 36121329 DOI: 10.1021/acs.orglett.2c02860] [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: 11/28/2022]
Abstract
In the presence of TiCl3, the reductive cyclization of tetrasubstituted enol esters bearing a 2-(ortho-nitroaryl) substituent affords 3-acyloxy-2,3-disubstituted indolenines in good yields. A domino process involving the partial reduction of nitro to a nitroso group followed by 5-center-6π-electrocyclization, 1,2-acyloxy migration, and the further reduction of the resulting nitrone intermediate accounts for the reaction outcome. The so-obtained indolenines are converted smoothly to 2,2-disubstituted oxindoles via a sequence of saponification and semipinacol rearrangement.
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Affiliation(s)
- Dina V Boyarskaya
- Laboratory of Synthesis and Natural Products (LSPN), Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LSPN, BCH 5304, Lausanne 1015, Switzerland
| | - Alberto Ongaro
- Laboratory of Synthesis and Natural Products (LSPN), Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LSPN, BCH 5304, Lausanne 1015, Switzerland
| | - Cyril Piemontesi
- Laboratory of Synthesis and Natural Products (LSPN), Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LSPN, BCH 5304, Lausanne 1015, Switzerland
| | - Qian Wang
- Laboratory of Synthesis and Natural Products (LSPN), Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LSPN, BCH 5304, Lausanne 1015, Switzerland
| | - Jieping Zhu
- Laboratory of Synthesis and Natural Products (LSPN), Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-SB-ISIC-LSPN, BCH 5304, Lausanne 1015, Switzerland
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5
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Zell D, Kingston C, Jermaks J, Smith SR, Seeger N, Wassmer J, Sirois LE, Han C, Zhang H, Sigman MS, Gosselin F. Stereoconvergent and -divergent Synthesis of Tetrasubstituted Alkenes by Nickel-Catalyzed Cross-Couplings. J Am Chem Soc 2021; 143:19078-19090. [PMID: 34735129 DOI: 10.1021/jacs.1c08399] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We report the development of a method to diastereoselectively access tetrasubstituted alkenes via nickel-catalyzed Suzuki-Miyaura cross-couplings of enol tosylates and boronic acid esters. Either diastereomeric product was selectively accessed from a mixture of enol tosylate starting material diastereomers in a convergent reaction by judicious choice of the ligand and reaction conditions. A similar protocol also enabled a divergent synthesis of each product isomer from diastereomerically pure enol tosylates. Notably, high-throughput optimization of the monophosphine ligands was guided by chemical space analysis of the kraken library to ensure a diverse selection of ligands was examined. Stereoelectronic analysis of the results provided insight into the requirements for reactive and selective ligands in this transformation. The synthetic utility of the optimized catalytic system was then probed in the stereoselective synthesis of various tetrasubstituted alkenes, with yields up to 94% and diastereomeric ratios up to 99:1 Z/E and 93:7 E/Z observed. Moreover, a detailed computational analysis and experimental mechanistic studies provided key insights into the nature of the underlying isomerization process impacting selectivity in the cross-coupling.
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Affiliation(s)
- Daniel Zell
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Cian Kingston
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Janis Jermaks
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Sleight R Smith
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Natalie Seeger
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Jana Wassmer
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Lauren E Sirois
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Chong Han
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Haiming Zhang
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Matthew S Sigman
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Francis Gosselin
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
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6
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Woltornist RA, Collum DB. Ketone Enolization with Sodium Hexamethyldisilazide: Solvent- and Substrate-Dependent E- Z Selectivity and Affiliated Mechanisms. J Am Chem Soc 2021; 143:17452-17464. [PMID: 34643382 PMCID: PMC10042305 DOI: 10.1021/jacs.1c06529] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ketone enolization by sodium hexamethyldisilazide (NaHMDS) shows a marked solvent and substrate dependence. Enolization of 2-methyl-3-pentanone reveals E-Z selectivities in Et3N/toluene (20:1), methyl-t-butyl ether (MTBE, 10:1), N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDTA)/toluene (8:1), TMEDA/toluene (4:1), diglyme (1:1), DME (1:22), and tetrahydrofuran (THF) (1:90). Control experiments show slow or nonexistent stereochemical equilibration in all solvents except THF. Enolate trapping with Me3SiCl/Et3N requires warming to -40 °C whereas Me3SiOTf reacts within seconds. In situ enolate trapping at -78 °C using preformed NaHMDS/Me3SiCl mixtures is effective in Et3N/toluene yet fails in THF by forming (Me3Si)3N. Rate studies show enolization via mono- and disolvated dimers in Et3N/toluene, disolvated dimers in TMEDA, trisolvated monomers in THF/toluene, and free ions with PMDTA. Density functional theory computations explore the selectivities via the E- and Z-based transition structures. Failures of theory-experiment correlations of ionic fragments were considerable even when isodesmic comparisons could have canceled electron correlation errors. Swapping 2-methyl-3-pentanone with a close isostere, 2-methylcyclohexanone, causes a fundamental change in the mechanism to a trisolvated-monomer-based enolization in THF.
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Affiliation(s)
- Ryan A Woltornist
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States
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7
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Affiliation(s)
- Hans‐Joachim Gais
- Institute of Organic Chemistry RWTH Aachen University Professor-Pirlet Strasse 1 52074 Aachen Germany
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8
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Abstract
The asymmetric alkylation of enolates is a particularly versatile method for the construction of α-stereogenic carbonyl motifs, which are ubiquitous in synthetic chemistry. Over the past several decades, the focus has shifted to the development of new catalytic methods that depart from classical stoichiometric stereoinduction strategies (e.g., chiral auxiliaries, chiral alkali metal amide bases, chiral electrophiles, etc.). In this way, the enantioselective alkylation of prochiral enolates greatly improves the step- and redox-economy of this process, in addition to enhancing the scope and selectivity of these reactions. In this review, we summarize the origin and advancement of catalytic enantioselective enolate alkylation methods, with a directed emphasis on the union of prochiral nucleophiles with carbon-centered electrophiles for the construction of α-stereogenic carbonyl derivatives. Hence, the transformative developments for each distinct class of nucleophile (e.g., ketone enolates, ester enolates, amide enolates, etc.) are presented in a modular format to highlight the state-of-the-art methods and current limitations in each area.
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Affiliation(s)
- Timothy B Wright
- Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada
| | - P Andrew Evans
- Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada.,Xiangya School of Pharmaceutical Sciences, Central South University, Changsha 410013, Hunan, P. R. of China
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9
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Mahato SK, Ohara N, Khake SM, Chatani N. Iridium(III)-Catalyzed Direct Intermolecular Chemoselective α-Amidation of Masked Aliphatic Carboxylic Acids with Dioxazolones via Nitrene Transfer. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01901] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Sanjit K. Mahato
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Nozomi Ohara
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Shrikant M. Khake
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Naoto Chatani
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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10
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Fulton TJ, Cusumano AQ, Alexy EJ, Du YE, Zhang H, Houk KN, Stoltz BM. Global Diastereoconvergence in the Ireland-Claisen Rearrangement of Isomeric Enolates: Synthesis of Tetrasubstituted α-Amino Acids. J Am Chem Soc 2020; 142:21938-21947. [PMID: 33320668 DOI: 10.1021/jacs.0c11480] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A dual experimental/theoretical investigation of the Ireland-Claisen rearrangement of tetrasubstituted α-phthalimido ester enolates to afford α-tetrasubstituted, β-trisubstituted α-amino acids (generally >20:1 dr) is described. For trans allylic olefins, the Z- and E-enol ethers proceed through chair and boat transition states, respectively. For cis allylic olefins, the trend is reversed. As a result, the diastereochemical outcome of the reaction is preserved regardless of the geometry of the enolate or the accompanying allylic olefin. We term this unique convergence of all possible olefin isomers global diastereoconvergence. This reaction manifold circumvents limitations in present-day technologies for the stereoselective enolization of α,α-disubstituted allyl esters. Density functional theory paired with state-of-the-art local coupled-cluster theory (DLPNO-CCSD(T)) was employed for the accurate determination of quantum mechanical energies.
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Affiliation(s)
- Tyler J Fulton
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Alexander Q Cusumano
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Eric J Alexy
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Yun E Du
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Haiming Zhang
- Small Molecule Process Chemistry, Genentech, Inc., South San Francisco, California 94080, United States
| | - K N Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Brian M Stoltz
- The Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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11
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Abstract
Installing quaternary stereogenic carbon is an arduous task of contemporary importance in the domain of asymmetric catalysis. To this end, an asymmetric allylic alkylation of α,α-disubstituted aldehydes by using allyl benzoate in the presence of Wilkinson's catalyst [Rh(Cl)(PPh3)3], (R)-BINOL–P(OMe) as the external ligand, and LiHMDS as the base has been reported to offer high enantioselectivity. The mechanistic details of this important reaction remain vague, which prompted us to undertake a detailed density functional theory (SMD(THF)/B3LYP-D3) investigation on the nature of the potential active catalyst, energetic features of the catalytic cycle, and the origin of high enantioselectivity. We note that a chloride displacement from the native Rh-phosphine [Rh(Cl)(PPh3)3] by BINOL–P(OMe) phosphite and an ensuing MeCl elimination can result in the in situ formation of a Rh-phosphonate [Rh(BINOL–P
Created by potrace 1.16, written by Peter Selinger 2001-2019
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O)(PPh3)3]. A superior energetic span (δE) noted with such a Rh-phosphonate suggests that it is likely to serve as an active catalyst. The uptake of allyl benzoate by the active catalyst followed by the turnover determining C–O bond oxidative addition furnishes a Rh-π-allyl intermediate, which upon interception by (Z)-Li-enolate (derived from α,α-disubstituted aldehyde) in the enantiocontrolling C–C bond generates a quaternary stereogenic center. The addition of the re prochiral face of the (Z)-Li-enolate to the Rh-bound allyl moiety leading to the R enantiomer of the product is found to be 2.4 kcal mol−1 more preferred over the addition through its si face. The origin of the stereochemical preference for the re face addition is traced to improved noncovalent interactions (NCIs) and less distortion in the enantiocontrolling C–C bond formation transition state than that in the si face addition. Computed enantioselectivity (96%) is in very good agreement with the experimental value (92%), so is the overall activation barrier (δE of 17.1 kcal mol−1), which is in conformity with room temperature reaction conditions. The origin of high enantioselectivity in the formation of quaternary stereogenic carbon.![]()
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Affiliation(s)
- Monika Pareek
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| | - Raghavan B Sunoj
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
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12
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Javorskis T, Karpavičienė I, Jurys A, Snarskis G, Bukšnaitienė R, Orentas E. An Enolate‐Structure‐Enabled Anionic Cascade Cyclization Reaction: Easy Access to Complex Scaffolds with Contiguous Six‐, Five‐, and Four‐Membered Rings. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202008317] [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: 11/06/2022]
Affiliation(s)
- Tomas Javorskis
- Department of Organic Chemistry Vilnius University Naugarduko 24 03225 Vilnius Lithuania
- Center for Physical Sciences and Technology Saulėtekio av. 3 10257 Vilnius Lithuania
| | - Ieva Karpavičienė
- Department of Organic Chemistry Vilnius University Naugarduko 24 03225 Vilnius Lithuania
| | - Arminas Jurys
- Department of Organic Chemistry Vilnius University Naugarduko 24 03225 Vilnius Lithuania
| | - Gustautas Snarskis
- Center for Physical Sciences and Technology Saulėtekio av. 3 10257 Vilnius Lithuania
| | - Rita Bukšnaitienė
- Department of Organic Chemistry Vilnius University Naugarduko 24 03225 Vilnius Lithuania
| | - Edvinas Orentas
- Department of Organic Chemistry Vilnius University Naugarduko 24 03225 Vilnius Lithuania
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13
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Javorskis T, Karpavičienė I, Jurys A, Snarskis G, Bukšnaitienė R, Orentas E. An Enolate-Structure-Enabled Anionic Cascade Cyclization Reaction: Easy Access to Complex Scaffolds with Contiguous Six-, Five-, and Four-Membered Rings. Angew Chem Int Ed Engl 2020; 59:20120-20128. [PMID: 32697013 DOI: 10.1002/anie.202008317] [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] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 07/12/2020] [Indexed: 01/07/2023]
Abstract
Catalyst-free addition of ketone enolate to non-activated multiple C-C bonds involves non-complementary reaction partners and typically requires super-basic conditions. On the other hand, highly aggregated or solvated enolates are not reactive enough to undergo direct addition to alkenes or alkynes. Herein, we report a new anionic cascade reaction for one-step assembly of intriguing molecular scaffolds possessing contiguous six-, five-, and four-membered rings, representing a formal [2+2] enol-allene cycloaddition. Reaction proceeds under very mild conditions and with excellent diastereoselectivity. Deeper mechanistic and computational studies revealed unusually slow proton transfer phenomenon in cyclic ketone intermediate and explained peculiar stereochemical outcome.
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Affiliation(s)
- Tomas Javorskis
- Department of Organic Chemistry, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania.,Center for Physical Sciences and Technology, Saulėtekio av. 3, 10257, Vilnius, Lithuania
| | - Ieva Karpavičienė
- Department of Organic Chemistry, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania
| | - Arminas Jurys
- Department of Organic Chemistry, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania
| | - Gustautas Snarskis
- Center for Physical Sciences and Technology, Saulėtekio av. 3, 10257, Vilnius, Lithuania
| | - Rita Bukšnaitienė
- Department of Organic Chemistry, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania
| | - Edvinas Orentas
- Department of Organic Chemistry, Vilnius University, Naugarduko 24, 03225, Vilnius, Lithuania
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14
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Abstract
The synthesis of fully substituted α-N-pyrrolyl and indolyl ketones via enantioselective palladium-catalyzed allylic alkylation is described. The acyclic ketones are alkylated in high yields with high enantioselectivities through the use of an electron-deficient phosphinooxazoline ligand, furnishing a highly congested and synthetically challenging stereocenter. The obtained alkylation products contain multiple reactive sites poised for additional functionalizations and diversification.
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Affiliation(s)
- Remi Lavernhe
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Eric J. Alexy
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Haiming Zhang
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Brian M. Stoltz
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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15
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Bigler R, Mack KA, Shen J, Tosatti P, Han C, Bachmann S, Zhang H, Scalone M, Pfaltz A, Denmark SE, Hildbrand S, Gosselin F. Asymmetric Hydrogenation of Unfunctionalized Tetrasubstituted Acyclic Olefins. Angew Chem Int Ed Engl 2020; 59:2844-2849. [PMID: 31794118 DOI: 10.1002/anie.201912640] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [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: 10/02/2019] [Indexed: 12/31/2022]
Abstract
Asymmetric hydrogenation has evolved as one of the most powerful tools to construct stereocenters. However, the asymmetric hydrogenation of unfunctionalized tetrasubstituted acyclic olefins remains the pinnacle of asymmetric synthesis and an unsolved challenge. We report herein the discovery of an iridium catalyst for the first, generally applicable, highly enantio- and diastereoselective hydrogenation of such olefins and the mechanistic insights of the reaction. The power of this chemistry is demonstrated by the successful hydrogenation of a wide variety of electronically and sterically diverse olefins in excellent yield and high enantio- and diastereoselectivity.
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Affiliation(s)
- Raphael Bigler
- Pharmaceutical Division, Small Molecules Technical Development, Department of Process Chemistry and Catalysis, F. Hoffmann-La Roche Ltd, 4070, Basel, Switzerland
| | - Kyle A Mack
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Jeff Shen
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Paolo Tosatti
- Pharmaceutical Division, Small Molecules Technical Development, Department of Process Chemistry and Catalysis, F. Hoffmann-La Roche Ltd, 4070, Basel, Switzerland
| | - Chong Han
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Stephan Bachmann
- Pharmaceutical Division, Small Molecules Technical Development, Department of Process Chemistry and Catalysis, F. Hoffmann-La Roche Ltd, 4070, Basel, Switzerland
| | - Haiming Zhang
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Michelangelo Scalone
- Pharmaceutical Division, Small Molecules Technical Development, Department of Process Chemistry and Catalysis, F. Hoffmann-La Roche Ltd, 4070, Basel, Switzerland
| | - Andreas Pfaltz
- Department of Chemistry, University of Basel, 4056, Basel, Switzerland
| | - Scott E Denmark
- Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, IL, 61801, USA
| | - Stefan Hildbrand
- Pharmaceutical Division, Small Molecules Technical Development, Department of Process Chemistry and Catalysis, F. Hoffmann-La Roche Ltd, 4070, Basel, Switzerland
| | - Francis Gosselin
- Department of Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
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16
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Bigler R, Mack KA, Shen J, Tosatti P, Han C, Bachmann S, Zhang H, Scalone M, Pfaltz A, Denmark SE, Hildbrand S, Gosselin F. Asymmetric Hydrogenation of Unfunctionalized Tetrasubstituted Acyclic Olefins. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201912640] [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] [Indexed: 01/08/2023]
Affiliation(s)
- Raphael Bigler
- Pharmaceutical DivisionSmall Molecules Technical DevelopmentDepartment of Process Chemistry and CatalysisF. Hoffmann-La Roche Ltd 4070 Basel Switzerland
| | - Kyle A. Mack
- Department of Small Molecule Process ChemistryGenentech, Inc. 1 DNA Way South San Francisco CA 94080 USA
| | - Jeff Shen
- Department of Small Molecule Process ChemistryGenentech, Inc. 1 DNA Way South San Francisco CA 94080 USA
| | - Paolo Tosatti
- Pharmaceutical DivisionSmall Molecules Technical DevelopmentDepartment of Process Chemistry and CatalysisF. Hoffmann-La Roche Ltd 4070 Basel Switzerland
| | - Chong Han
- Department of Small Molecule Process ChemistryGenentech, Inc. 1 DNA Way South San Francisco CA 94080 USA
| | - Stephan Bachmann
- Pharmaceutical DivisionSmall Molecules Technical DevelopmentDepartment of Process Chemistry and CatalysisF. Hoffmann-La Roche Ltd 4070 Basel Switzerland
| | - Haiming Zhang
- Department of Small Molecule Process ChemistryGenentech, Inc. 1 DNA Way South San Francisco CA 94080 USA
| | - Michelangelo Scalone
- Pharmaceutical DivisionSmall Molecules Technical DevelopmentDepartment of Process Chemistry and CatalysisF. Hoffmann-La Roche Ltd 4070 Basel Switzerland
| | - Andreas Pfaltz
- Department of ChemistryUniversity of Basel 4056 Basel Switzerland
| | - Scott E. Denmark
- Roger Adams LaboratoryDepartment of ChemistryUniversity of Illinois Urbana IL 61801 USA
| | - Stefan Hildbrand
- Pharmaceutical DivisionSmall Molecules Technical DevelopmentDepartment of Process Chemistry and CatalysisF. Hoffmann-La Roche Ltd 4070 Basel Switzerland
| | - Francis Gosselin
- Department of Small Molecule Process ChemistryGenentech, Inc. 1 DNA Way South San Francisco CA 94080 USA
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17
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Woltornist RA, Ma Y, Algera RF, Zhou Y, Zhang Z, Collum DB. Structure, Reactivity, and Synthetic Applications of Sodium Diisopropylamide. SYNTHESIS-STUTTGART 2020; 52:1478-1497. [PMID: 34349297 DOI: 10.1055/s-0039-1690846] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [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: 12/11/2022]
Abstract
The 60-year history of sodium diisopropylamide (NaDA) is described herein. We review various preparations, solvent-dependent stabilities, and solution structures. Synthetic applications of NaDA reported to date are framed by a mechanism-driven approach, emphasizing selectivities when appropriate. We conclude with examples beyond metalation in which NaDA plays a central role and a few thoughts on where future applications could be focused.
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Affiliation(s)
- Ryan A Woltornist
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Russell F Algera
- Pfizer Worldwide Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Yuhui Zhou
- Frontage Laboratories, Inc., 75 E Uwchlan Avenue, Suite 100, Exton, PA, 19341
| | - Zirong Zhang
- Department of Chemistry, University of Michigan, CHEM 3614 930 North University Ave, Ann Arbor, MI, 48109
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301.,Pfizer Worldwide Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States.,Frontage Laboratories, Inc., 75 E Uwchlan Avenue, Suite 100, Exton, PA, 19341.,Department of Chemistry, University of Michigan, CHEM 3614 930 North University Ave, Ann Arbor, MI, 48109
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18
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Lavernhe R, Alexy EJ, Zhang H, Stoltz BM. Palladium-Catalyzed Enantioselective Decarboxylative Allylic Alkylation of Protected Benzoin-Derived Enol Carbonates. Adv Synth Catal 2019; 362:344-347. [PMID: 33692657 DOI: 10.1002/adsc.201901281] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [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: 01/05/2023]
Abstract
The enantioselective palladium-catalyzed decarboxylative allylic alkylation of fully substituted α-hydroxy acyclic enol carbonates providing tetrasubstituted benzoin derivatives is reported. Investigation into the transformation revealed that preparation of the starting material as a single enolate isomer is crucial for optimal enantioselectivity. The obtained alkylation products contain multiple reactive sites that can be utilized toward the synthesis of stereochemically rich derivatives. COMMUNICATION.
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Affiliation(s)
- Rémi Lavernhe
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Eric J Alexy
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Haiming Zhang
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Brian M Stoltz
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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19
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Fulton TJ, Wu B, Alexy EJ, Zhang H, Stoltz BM. Palladium-catalyzed α,β-dehydrogenation of acyclic ester equivalents promoted by a novel electron deficient phosphinooxazoline ligand. Tetrahedron 2019; 75:4104-4109. [PMID: 32255844 DOI: 10.1016/j.tet.2019.05.065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [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: 11/30/2022]
Abstract
A unique example of Pd-catalyzed decarboxylative dehydrogenation of fully substituted N-acyl allyl enol carbonates is enabled by a new electron deficient phosphinooxazoline (PHOX) ligand. The reaction proceeds from the Z-enol carbonate to provide dehydrogenation products exclusively in high E/Z selectivity, while the E-enol carbonate provides the α-allylation product with only minor dehydrogenation. The reaction proceeds with a broad scope of (Z)-enol carbonates derived from N-acyl indoles to furnish acyclic formal α,β-unsaturated ester equivalents.
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Affiliation(s)
- Tyler J Fulton
- Warren and Katharine Schlinger Laboratory of Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, California 91125, United States of America
| | - Brenda Wu
- Warren and Katharine Schlinger Laboratory of Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, California 91125, United States of America
| | - Eric J Alexy
- Warren and Katharine Schlinger Laboratory of Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, California 91125, United States of America
| | - Haiming Zhang
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States of America
| | - Brian M Stoltz
- Warren and Katharine Schlinger Laboratory of Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd, Pasadena, California 91125, United States of America
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20
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Affiliation(s)
- Zhi‐Chao Cao
- Department of ChemistryFudan University Shanghai 200433 China
- College of Chemistry and Molecular EngineeringPeking University Beijing 100871 China
| | - Pei‐Lin Xu
- College of Chemistry and Molecular EngineeringPeking University Beijing 100871 China
| | - Qin‐Yu Luo
- College of Chemistry and Molecular EngineeringPeking University Beijing 100871 China
| | - Xiao‐Lei Li
- College of Chemistry and Molecular EngineeringPeking University Beijing 100871 China
| | - Da‐Gang Yu
- College of ChemistrySichuan University Chengdu Sichuan 610064 China
| | - Huayi Fang
- Department of ChemistryFudan University Shanghai 200433 China
| | - Zhang‐Jie Shi
- Department of ChemistryFudan University Shanghai 200433 China
- College of Chemistry and Molecular EngineeringPeking University Beijing 100871 China
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21
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Majhi J, Turnbull BWH, Ryu H, Park J, Baik MH, Evans PA. Dynamic Kinetic Resolution of Alkenyl Cyanohydrins Derived from α,β-Unsaturated Aldehydes: Stereoselective Synthesis of E-Tetrasubstituted Olefins. J Am Chem Soc 2019; 141:11770-11774. [DOI: 10.1021/jacs.9b04384] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jadab Majhi
- Department of Chemistry, Queen’s University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada
| | - Ben W. H. Turnbull
- Department of Chemistry, Queen’s University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada
| | - Ho Ryu
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
- Center for
Catalytic
Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - Jiyong Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
- Center for
Catalytic
Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - Mu-Hyun Baik
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
- Center for
Catalytic
Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea
| | - P. Andrew Evans
- Department of Chemistry, Queen’s University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada
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22
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Alexy EJ, Fulton TJ, Zhang H, Stoltz BM. Palladium-catalyzed enantioselective decarboxylative allylic alkylation of fully substituted N-acyl indole-derived enol carbonates. Chem Sci 2019; 10:5996-6000. [PMID: 31360407 PMCID: PMC6566452 DOI: 10.1039/c9sc01726g] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [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: 04/08/2019] [Accepted: 04/26/2019] [Indexed: 01/06/2023] Open
Abstract
The first enantioselective Pd-catalyzed decarboxylative allylic alkylation of fully substituted N-acyl indole-derived enol carbonates generates acyclic all-carbon quaternary stereocenters in excellent yields (up to 99%) and enantioselectivities (up to 98% ee) using a new electron-deficient phosphinoxazoline (PHOX) ligand.
The first enantioselective palladium-catalyzed decarboxylative allylic alkylation of fully substituted N-acyl indole-derived enol carbonates forming acyclic all-carbon quaternary stereocenters is reported. Excellent yields up to 99% and enantioselectivities up to 98% ee are obtained through the use of a new electron-deficient phosphinoxazoline (PHOX) ligand. Control of substrate enolate geometry is crucial for high selectivity. The obtained α-quaternary N-acyl indoles are formal ester equivalents, and represent a useful handle for further synthetic transformations.
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Affiliation(s)
- Eric J Alexy
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering , Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , CA 91125 , USA .
| | - Tyler J Fulton
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering , Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , CA 91125 , USA .
| | - Haiming Zhang
- Small Molecule Process Chemistry, Genentech, Inc. , 1 DNA Way , South San Francisco , CA 94080 , USA .
| | - Brian M Stoltz
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering , Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , CA 91125 , USA .
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23
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Rao KS, St-Jean F, Kumar A. Quantitation of a Ketone Enolization and a Vinyl Sulfonate Stereoisomer Formation Using Inline IR Spectroscopy and Modeling. Org Process Res Dev 2019. [DOI: 10.1021/acs.oprd.9b00042] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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24
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Savage S, McClory A, Zhang H, Cravillion T, Lim NK, Masui C, Robinson SJ, Han C, Ochs C, Rege PD, Gosselin F. Synthesis of Selective Estrogen Receptor Degrader GDC-0810 via Stereocontrolled Assembly of a Tetrasubstituted All-Carbon Olefin. J Org Chem 2018; 83:11571-11576. [DOI: 10.1021/acs.joc.8b01551] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
| | | | | | | | | | | | | | | | - Christoph Ochs
- Department of Process Chemistry and Catalysis, F. Hoffmann-La Roche AG, Grenzacherstrasse 124, CH-4070 Basel, Switzerland
| | - Pankaj D. Rege
- Department of Process Chemistry and Catalysis, F. Hoffmann-La Roche AG, Grenzacherstrasse 124, CH-4070 Basel, Switzerland
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25
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Alexy EJ, Zhang H, Stoltz BM. Catalytic Enantioselective Synthesis of Acyclic Quaternary Centers: Palladium-Catalyzed Decarboxylative Allylic Alkylation of Fully Substituted Acyclic Enol Carbonates. J Am Chem Soc 2018; 140:10109-10112. [PMID: 30049213 PMCID: PMC6103296 DOI: 10.1021/jacs.8b05560] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The first enantioselective palladium-catalyzed decarboxylative allylic alkylation of fully substituted acyclic enol carbonates providing linear α-quaternary ketones is reported. Investigation into the reaction revealed that the use of an electron-deficient phosphinooxazoline ligand renders the enolate geometry of the starting material inconsequential, with the same enantiomer of product obtained in the same level of selectivity regardless of the starting ratio of enolates. As a result, a general method toward acyclic all-carbon quaternary stereocenters has been developed.
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Affiliation(s)
- Eric J. Alexy
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Haiming Zhang
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Brian M. Stoltz
- Warren and Katharine Schlinger Laboratory for Chemistry and Chemical Engineering, Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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26
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Tayama E, Nishio R, Kobayashi Y. Base-promoted diastereoselective α-alkylation of borane N-((S)-1'-phenylethyl)azetidine-2-carboxylic acid ester complexes. Org Biomol Chem 2018; 16:5833-5845. [PMID: 30070285 DOI: 10.1039/c8ob01395k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The base-promoted α-alkylation of N-((S)-1-phenylethyl)azetidine-2-carboxylic acid esters 1 was investigated. The use of diastereomerically pure borane complexes 3 as substrates, which are easily prepared from 1, dramatically improved the yields and diastereoselectivities of α-alkylated products 2. For example, the treatment of tert-butyl ester (1S,2S,1'S)-3a with 2.4 equivalents of lithium bis(trimethysilyl)amide (LiHMDS) at 0 °C followed by 2.6 equivalents of benzyl bromide afforded α-benzylated (2S,1'S)-2aa in 90% yield as almost a single diastereomer. Our method enables the production of optically active α-substituted azetidine-2-carboxylic acid esters starting from commercially available (S)-1-phenylethylamine, which is one of the least expensive chiral compounds.
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Affiliation(s)
- Eiji Tayama
- Department of Chemistry, Faculty of Science, Niigata University, Niigata, 950-2181, Japan.
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