Synthesis of 3,4-Disubstituted Piperidines by Carbonyl Ene and Prins Cyclizations: Switching between Kinetic and Thermodynamic Control with Brønsted and Lewis Acid Catalysts
作者:Jodi T. Williams、Perdip S. Bahia、Benson M. Kariuki、Neil Spencer、Douglas Philp、John S. Snaith
DOI:10.1021/jo052532+
日期:2006.3.1
to cis and trans 3,4-disubstituted piperidines is described. Carbonyl ene cyclization of aldehydes 4a−e catalyzed by MeAlCl2 in refluxing chloroform afforded the trans piperidines 7a−e with diastereomeric ratios of up to 93:7, while aldehyde 4f afforded solely the cis product 6f, which was resistant to isomerization to the trans isomer. It was demonstrated for 4a that the cyclization catalyzed by a