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Cinchona Amino-Thiocarbamate Catalyzed Bromolactonization
L. Zhou, C. K. Tan, X. Jiang, F. Chen, Y.-Y. Yeung*
National University of Singapore, Singapore
21 December 2010 (online)
A cinchonine-derived thiocarbamate is reported to efficiently catalyze the bromolactonization of 4-substituted 4-pentenoic acids to give the corresponding γ-lactones in high yields and good enantioselectivities. Catalyst 1 is presumed to act as a bifunctional catalyst, simultaneously activating NBS with the Lewis-basic thiocarbamate and the carboxylic acid with the Brønsted-basic tertiary amine. The utility of the products is demonstrated and initial mechanistic studies, supporting the suggested bifunctional mechanism, are provided.