Inner Workings of a Cinchona Alkaloid Catalyzed Oxa??Michael Cyclization: Evidence for a Concerted Hydrogen??Bond??Network Mechanism

L Hintermann, J Ackerstaff…

Index: Hintermann, Lukas; Ackerstaff, Jens; Boeck, Florian Chemistry - A European Journal, 2013 , vol. 19, # 7 p. 2311 - 2321

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Citation Number: 27

Abstract

Abstract Cinchona alkaloids catalyze the oxa-Michael cyclization of 4-(2-hydroxyphenyl)-2- butenoates to benzo-2, 3-dihydrofuran-2-yl acetates and related substrates in up to 99% yield and 91% ee (ee= enantiomeric excess). Catalyst and substrate variation studies reveal an important role of the alkaloid hydroxy group in the reaction mechanism, but not in the sense of a hydrogen-bonding activation of the carbonyl group of the substrate as assumed ...