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Theoretical Studies on the Mechanism of the Michael Addition Reaction Catalyzed by a Thiourea‐Cinchona‐Amine: Triple Activation
Author(s) -
Zhou MeiJuan,
Li Yun,
Dang Li
Publication year - 2015
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.201500183
Subject(s) - chemistry , imine , catalysis , thiourea , michael reaction , protonation , cinchona , amine gas treating , reaction mechanism , organic chemistry , organocatalysis , photochemistry , medicinal chemistry , combinatorial chemistry , enantioselective synthesis , ion
This paper attempts to illuminate the mechanism of the catalytic Michael addition of 2,4‐pentanedione with acrylaldehyde mediated by a thiourea‐cinchona‐amine catalyst via density functional theory calculations. The calculated results show that the C−C coupling easily occurs once the electronegative and electropositive sites of the reactants are generated by the catalyst. However, the previously proposed mechanism with the formation of an imine from the carbonyl group of reactants and the amine group of catalyst fails due to high reaction barriers for both the formation of the imine and the hydrolysis of the imine with water in order to regenerate the catalyst. Instead, the reaction pathways going through the protonation of the amine in the catalyst and formation of hydrogen bonds between the reactants and catalyst have smaller barriers. Our study will be helpful in designing new catalysts or extending the substrate scope of the reaction.