Stereoconvergent 1,4-Addition Reaction of 5H-Oxazol-4-ones with E,Z Isomeric Mixture of Alkylidene β-Ketoesters Catalyzed by Chiral Guanidines.

A 1,4-addition reaction of 5H-oxazol-4-ones to alkylidene β-ketoesters, which was catalyzed by using chiral guanidines via a dynamic kinetic resolution process that involved geometric isomerization of the alkylidene β-ketoesters, was developed. This method allowed using E,Z isomeric mixture of various acyclic alkylidene β-ketoesters to obtain the products stereoselectively. The relation between the geometry and the stereoselectivity of products was investigated, and the derivatization of the products to the corresponding α-acyl-γ-lactone was performed.