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Highly Enantioselective Reactions of Cyclohexanone and β , γ ‐Unsaturated α ‐Keto Ester: The Tuning of Chemo‐selectivities by Secondary and Primary Amine Catalysts
Author(s) -
Wei Jianwei,
Guo Wengang,
Zhou Xin,
Du Xin,
Liu Yan,
Li Can
Publication year - 2014
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201400431
Subject(s) - chemistry , cyclohexanone , amine gas treating , catalysis , primary (astronomy) , aldol reaction , organic chemistry , enantioselective synthesis , steric effects , solvent , physics , astronomy
A series of of amphiphilic imidazole based secondary and primary amine catalysts were synthesized and shown to be very effective with an acid cocatalyst for the asymmetric reaction of cyclohexanone to β , γ ‐unsaturated α ‐keto ester. Interestingly, primary and secondary amine catalysts show different regio‐selectivities in this reaction. Under the catalysis of secondary amine 1 , excellent enantioselectivities were observed for the products from direct 3+3 reactions of cyclohexanone with β , γ ‐unsaturated α ‐keto esters using water as the solvent. Moreover, the same reactants catalyzed by the primary amines 2 lead to the aldol reactions, affording the corresponding products with high diastereoselectivities and up to 97% ee . Theoretical studies on the transition states by using a model in gas phase revealed that steric effect plays an important role on different chemo‐selective induction between the secondary amine 1 and primary amine 2 .