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Yuan D, Goodfellow AS, Kasten K, Duan Z, Kang T, Cordes DB, McKay AP, Bühl M, Boyce GR, Smith AD. Understanding divergent substrate stereoselectivity in the isothiourea-catalysed conjugate addition of cyclic α-substituted β-ketoesters to α,β-unsaturated aryl esters. Chem Sci 2023; 14:14146-14156. [PMID: 38098722 PMCID: PMC10717594 DOI: 10.1039/d3sc05470e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2023] [Accepted: 11/20/2023] [Indexed: 12/17/2023] Open
Abstract
The development of enantioselective synthetic methods capable of generating vicinal stereogenic centres, where one is tetrasubstituted (such as either an all-carbon quaternary centre or where one or more substituents are heteroatoms), is a recognised synthetic challenge. Herein, the enantioselective conjugate addition of a range of carbo- and heterocyclic α-substituted β-ketoesters to α,β-unsaturated aryl esters using the isothiourea HyperBTM as a Lewis base catalyst is demonstrated. Notably, divergent diastereoselectivity is observed through the use of either cyclopentanone-derived or indanone-derived substituted β-ketoesters with both generating the desired stereodefined products with high selectivity (>95 : 5 dr, up to 99 : 1 er). The scope and limitations of these processes are demonstrated, alongside application on gram scale. The origin of the divergent substrate selectivity has been probed through the use of DFT-analysis, with preferential orientation driven by dual stabilising CH⋯O interactions. The importance of solvation with strongly polar transition-states is highlighted and the SMD solvation model is demonstrated to capture solvation effects reliably.
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Affiliation(s)
- Ding Yuan
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
- School of Biological and Chemical Engineering, Panzhihua University Panzhihua 617000 China
| | - Alister S Goodfellow
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Kevin Kasten
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Zhuan Duan
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Tengfei Kang
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - David B Cordes
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Aidan P McKay
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Michael Bühl
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Gregory R Boyce
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
- Department of Chemistry and Physics, Florida Gulf Coast University Fort Myers Florida 33965 USA
- Department of Chemistry and Biochemistry, East Stroudsburg University East Stroudsburg Pennsylvania 18301 USA
| | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
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Nimmo AJ, Bitai J, Young CM, McLaughlin C, Slawin AMZ, Cordes DB, Smith AD. Enantioselective isothiourea-catalysed reversible Michael addition of aryl esters to 2-benzylidene malononitriles. Chem Sci 2023; 14:7537-7544. [PMID: 37449062 PMCID: PMC10337745 DOI: 10.1039/d3sc02101g] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 05/31/2023] [Indexed: 07/18/2023] Open
Abstract
Catalytic enantioselective transformations usually rely upon optimal enantioselectivity being observed in kinetically controlled reaction processes, with energy differences between diastereoisomeric transition state energies translating to stereoisomeric product ratios. Herein, stereoselectivity resulting from an unusual reversible Michael addition of an aryl ester to 2-benzylidene malononitrile electrophiles using an isothiourea as a Lewis base catalyst is demonstrated. Notably, the basicity of the aryloxide component and reactivity of the isothiourea Lewis base both affect the observed product selectivity, with control studies and crossover experiments indicating the feasibility of a constructive reversible Michael addition from the desired product. When this reversible addition is coupled with a crystallisation-induced diastereomer transformation (CIDT) it allows isolation of products in high yield and stereocontrol (14 examples, up to 95 : 5 dr and 99 : 1 er). Application of this process to gram scale, plus derivatisations to provide further useful products, is demonstrated.
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Affiliation(s)
- Alastair J Nimmo
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Jacqueline Bitai
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Claire M Young
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Calum McLaughlin
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Alexandra M Z Slawin
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - David B Cordes
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
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Bitai J, Nimmo AJ, Slawin AMZ, Smith AD. Cooperative Palladium/Isothiourea Catalyzed Enantioselective Formal (3+2) Cycloaddition of Vinylcyclopropanes and α,β-Unsaturated Esters. Angew Chem Int Ed Engl 2022; 61:e202202621. [PMID: 35389553 PMCID: PMC9324207 DOI: 10.1002/anie.202202621] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Indexed: 12/15/2022]
Abstract
A protocol for the enantioselective synthesis of substituted vinylcyclopentanes has been realised using cooperative palladium and isothiourea catalysis. Treatment of vinylcyclopropanes with Pd(PPh3 )4 generates a zwitterionic π-allyl palladium intermediate that intercepts a catalytically generated α,β-unsaturated acyl ammonium species prepared from the corresponding α,β-unsaturated para-nitrophenyl ester and the isothiourea (R)-BTM. Intermolecular formal (3+2) cycloaddition between these reactive intermediates generates functionalised cyclopentanes in generally good yields and excellent diastereo- and enantiocontrol (up to >95 : 5 dr, 97 : 3 er), with the use of LiCl as an additive proving essential for optimal stereocontrol. To the best of our knowledge a dual transition metal/organocatalytic process involving α,β-unsaturated acyl ammonium intermediates has not been demonstrated previously.
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Affiliation(s)
- Jacqueline Bitai
- EaStCHEM, School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
| | - Alastair J Nimmo
- EaStCHEM, School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
| | - Alexandra M Z Slawin
- EaStCHEM, School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
| | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
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Bitai J, Nimmo AJ, Slawin AMZ, Smith AD. Cooperative Palladium/Isothiourea Catalyzed Enantioselective Formal (3+2) Cycloaddition of Vinylcyclopropanes and a,b‐Unsaturated Esters. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202202621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
| | | | | | - Andrew David Smith
- University of St Andrews School of Chemistry North Haugh FIFE, KY10 3TH St. Andrews UNITED KINGDOM
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McLaughlin C, Bitai J, Barber LJ, Slawin AMZ, Smith AD. Catalytic enantioselective synthesis of 1,4-dihydropyridines via the addition of C(1)-ammonium enolates to pyridinium salts. Chem Sci 2021; 12:12001-12011. [PMID: 34667566 PMCID: PMC8457386 DOI: 10.1039/d1sc03860e] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 08/05/2021] [Indexed: 12/30/2022] Open
Abstract
The regio- and stereoselective addition of C(1)-ammonium enolates - generated in situ from aryl esters and the isothiourea catalyst (R)-BTM - to pyridinium salts bearing an electron withdrawing substituent in the 3-position allows the synthesis of a range of enantioenriched 1,4-dihydropyridines. This represents the first organocatalytic approach to pyridine dearomatisation using pronucleophiles at the carboxylic acid oxidation level. Optimisation studies revealed a significant solvent dependency upon product enantioselectivity, with only toluene providing significant asymmetric induction. Using DABCO as a base also proved beneficial for product enantioselectivity, while investigations into the nature of the counterion showed that co-ordinating bromide or chloride substrates led to higher product er than the corresponding tetrafluoroborate or hexafluorophosphate. The scope and limitations of this process are developed, with enantioselective addition to 3-cyano- or 3-sulfonylpyridinium salts giving the corresponding 1,4-dihydropyridines (15 examples, up to 95 : 5 dr and 98 : 2 er).
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Affiliation(s)
- Calum McLaughlin
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Jacqueline Bitai
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Lydia J Barber
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Alexandra M Z Slawin
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
| | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St Andrews St Andrews Fife KY16 9ST UK
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Dai RH, Han L, Wang Q, Tian SK. Strain-release C-C bond cleavage enables the [2,3]-sigmatropic rearrangement of tertiary allylamines. Chem Commun (Camb) 2021; 57:8449-8451. [PMID: 34342309 DOI: 10.1039/d1cc03141d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A new strategy has been established for the [2,3]-sigmatropic rearrangement of quaternary allylammonium ylides, generated in situ from tertiary allylamines and a bicyclo[1.1.0]butane via strain-release C-C bond cleavage. A range of tertiary allylamines with an acidic α-C-H bond participated in the 1-sulfonylbicyclo[1.1.0]butane-mediated [2,3]-sigmatropic rearrangement, delivering structurally diverse N-cyclobutyl homoallylamines in moderate to excellent yields.
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Affiliation(s)
- Rui-Han Dai
- Hefei National Laboratory for Physical Sciences at the Microscale, Center for Excellence in Molecular Synthesis (CAS), and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China.
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