A copper-catalyzed diastereoselective O-transfer reaction of N-vinyl-alpha,beta-unsaturated nitrones with ketenes into gamma-lactones through [5+2] cycloaddition and N-O bond cleavage

摘要

A general protocol for the construction of novel densely functionalized gamma-lactones was developed in good to excellent yields with high diastereoselectivity from easily available N-vinyl-alpha,beta-unsaturated nitrones and ketenes. The reaction involves copper-catalyzed [5 + 2] cycloaddition, N-O bond cleavage, 6 pi electron cyclization, and aromatization to afford various gamma-(pyridin-2-yl)lactones over four step transformations in a single flask. The present method features mild reaction conditions, high atom economy, high regio- and diastereoselectivity, diversity of gamma-lactones, and a new application of the O-transfer reaction.