Enantioselective [3 + 2] cycloaddition and rearrangement of thiazolium salts to synthesize thiazole and 1,4-thiazine derivatives

Abstract

Highly efficient asymmetric [3 + 2] cycloaddition reactions of thiazolium salts with a variety of electron-deficient 2-π components were achieved by chiral N,N′-dioxide/metal complex catalysts, providing a convenient route to access enantioenriched hydropyrrolo-thiazoles. The oxathiazine and sulfinate could be readily obtained by the oxidation of the hydropyrrolo-thiazole. Moreover, through ingenious collaboration of chiral catalysts with basic additives, the first cascade cycloaddition/rearrangement reaction with β,γ-unsaturated α-ketoesters was realized, and various pyrrolo-[1,4]thiazine derivatives were afforded in excellent results.