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Exploiting the Imidazolium Effect in Base‐free Ammonium Enolate Generation: Synthetic and Mechanistic Studies
Author(s) -
Young Claire M.,
Stark Daniel G.,
West Thomas H.,
Taylor James E.,
Smith Andrew D.
Publication year - 2016
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201608046
Subject(s) - ammonium , base (topology) , chemistry , enantioselective synthesis , stereoselectivity , michael reaction , catalysis , organic chemistry , combinatorial chemistry , mathematical analysis , mathematics
Abstract N‐Acyl imidazoles and catalytic isothiourea hydrochloride salts function as ammonium enolate precursors in the absence of base. Enantioselective Michael addition–cyclization reactions using different α,β‐unsaturated Michael acceptors have been performed to form dihydropyranones and dihydropyridinones with high stereoselectivity. Detailed mechanistic studies using RPKA have revealed the importance of the “imidazolium” effect in ammonium enolate formation and have highlighted key differences with traditional base‐mediated processes.