Cope, A. C. et al. J. Am. Chem. Soc. 1940, 62, 441. Lutz, R. P. et al. Chem. Rev. 1984, 84, 205.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Cope Rearrangement
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[3,3]-Sigmatropic Rearrangements: Enantioselective Claisen Rearrangement
The Claisen rearrangement is a symmetry-allowed pericyclic reaction that proceeds via a six-membered transition state (1→TS→2). Due to the general preference for a stereoelectronically favored chair-like transition state, the stereochemical information in the substrates is transferred to the products in a predictable manner.
Lewis acidic metal complexes of Al, B, Mg and Cu...
Drawback: high loading of these catalysts Geometry of enolate plays a key role Corey, E. J. et al. J. Am. Chem. Soc. 1991, 113, 4026-4028.
Because the cope rearrangement is reversible, synthetic utility requires a favorable equilibrium. In the variants of the cope rearrangement shown above, driving force arises from relief of ring-strain, cleavage of a weak N-N, or N-O bond or ion-stabilization.
Chin, J. et al. Org. Lett. 2009, 11, 5258.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Cope Rearrangement
Tandem cyclopropanation/Cope rearrangement (TCCR) between vinylcarbenoids and pyrroles Davies, H. M. L. et al. J. Am. Chem. Soc. 2007, 129, 10312.
Pd-A provided the same results as the in situ procedure.
List, B. et al. Angew. Chem. Int. Ed. 2011, 50, 9752-9755.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Cope Rearrangement
6
[3,3]-Sigmatropic Rearrangements: Enantioselective Claisen Rearrangement Lewis acid-catalyzed enantioselective acyl-Claisen reaction: variant of the Bellus reaction
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[2,3]-Sigmatropic Rearrangements
[2,3]-sigmatropic rearrangements are synthetically useful since they can lead to:
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[3,3]-Sigmatropic Rearrangements: Enantioselective Cope Rearrangement catalytic enantioselective Cope rearrangements as part of a tandem process
Rueping, M. Angew. Chem. Int. Ed. 2008, 47, 10090.
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大纲
手性基本概念 （手性、选择性、手性测定、动力学拆分） 羰基化合物：alpha-烷基化、芳基化、卤化 Aldol反应 C=O加成, C=N加成, C=C加成(Michael加成) 环化反应：DA；3+2；2+2；等等；PK；Nazarov；烯烃复分解 氧化反应：双键（环氧化、双羟化、羟胺化、氮杂环丙化、环丙烷化、卤化）；醇（动力学 拆分）；羰基 氢化及还原反应：C=C; C=O; C=N; 芳香化合物 偶联反应 烯丙基取代反应 （Pd, Ir, Ru, Rh, Cu） 碳氢键直接官能化：傅克反应、氧化偶联、碳氢键活化 重排反应 有机催化：手性胺（enamine; iminium; SOMO; cascade; photocatalysis）；Lewis base (HSiCl3还原）；亲核催化（手性膦手性胺 氮杂环卡宾MBH；环化反应)；手性布朗斯特酸； NHC极性反转反应
反应分类-----活化模式
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不对称σ重排反应
1. [3,3]-Sigmatropic Rearrangements Claisen and related rearrangements Cope rearrangements 2. [2,3]-Sigmatropic Rearrangements Neutral and Anionic type
a high level of chirality transfer
Morken, J. P. et al. Org. Lett. 2005, 7, 4867.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Claisen Rearrangement
The cope rearrangement is a symmetry-allowed pericycle reaction that proceeds via that six-membered, chair-like transition state (1→TS→2) in which the steric repulsion is minimal.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Cope Rearrangement Most synthetic examples utilize starting materials with one or two chiral centers on the six-carbon path. Some examples involve a chiral controller group.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Claisen Rearrangement
enantioselective Overman rearrangement: asymmetric counteranion-directed catalysis
Mechanism
MacMillan, D. W. et al. J. Am. Chem. Soc. 20tropic Rearrangements: Enantioselective Claisen Rearrangement reductive Claisen reaction:
Bode, J. W. et al. J. Am. Chem. Soc. 2010, 132, 8810.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Claisen Rearrangement enantioselective Overman rearrangement: first report J. Org. Chem. 1997, 62, 1449
Claisen, L. Ber. Dtsch. Chem. Ges. 1913, 45, 3157-3166. Castro, A. M. M. Chem. Rev. 2004, 104, 2939-3002.
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[3,3]-Sigmatropic Rearrangements: Enantioselective Claisen Rearrangement A non-concerted stepwise pathway is also possible (via e.g., ion pair or radical), depending on the substituents and reaction conditions. A number of variants of this rearrangement have been developed, Including:
(E)-allylic trichloroacetimidates, up to 98% ee and high yields; low yields and moderate enantioselectivity for (Z)-substrates the first truly practical method for transforming prochiral allylic alcohols to enantioenriched allylic amines JACS, 2003, 125, 12431; JACS, 2007, 129, 5031 (mechanism)