Palladium-catalyzed stereoselective (3 + 2) cycloaddition of vinylethylene carbonates with cyclic N-sulfonyl ketimines

Abstract

A diastereoselective (3 + 2) cycloaddition of N-sulfonyl ketimines with vinylethylene carbonates (VECs) in the presence of Pd₂dba₃·CHCl₃ and PPh₃ has been developed. The reaction of various substituted VECs and diverse cyclic N-sulfonyl ketimines proceeded smoothly under mild conditions, giving highly functionalized oxazolidine frameworks in good to excellent yields with moderate to good diastereoselectivities. With the use of spiroketal-based diphosphine SKP as a chiral ligand, an asymmetric version of the current (3 + 2) cycloaddition was achieved, and chiral products were obtained in >99% ee in most cases.