Construction of N,S-polyheterocyclic scaffolds via asymmetric [3 + 2] cycloaddition of benzothiazolium salts catalyzed by a chiral-at-metal rhodium complex

Abstract

Highly efficient asymmetric [3 + 2] cycloaddition reactions of benzothiazolium salts with α,β-unsaturated 2-acyl imidazoles were achieved by a chiral-at-metal rhodium complex catalyst. Enantioenriched hydropyrrolo-thiazole derivatives bearing four contiguous tertiary stereocenters were obtained in generally high yields with good stereoselectivities (up to >20 : 1 dr, 99% ee). This reaction not only represents a good example of metal-catalyzed [3 + 2] cycloaddition reactions of benzothiazolium salts but also provides a convenient route to construct enantioenriched N,S-polyheterocyclic scaffolds.