No abstract

A sequential procedure for the synthesis of 2,5-disubstituted thiazoles from terminal alkynes, sulfonyl azides, and thionoesters is reported. A copper(I)-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with thionoesters in the presence of a rhodium(II) catalyst. The resulting 3-sulfonyl-4-thiazolines subsequently aromatize into the corresponding 2,5-disubstituted thiazoles by elimination of the sulfonyl group.

N-Sulfonyl-1,2,3-triazoles react with thioesters in the presence of ar hodium(II) catalyst to produce b-sulfanyl enamides in as tereoselective manner.T he reaction proceeds through generation of an a-imino rhodium carbene complex, nucleophilic addition of the sulfur atom of athioester onto the carbenoid carbon atom, and subsequent intramolecular migration of the acyl group from the sulfur atom to the imino nitrogen atom. The method is successfully applied to ar ingexpansion reaction of thiolactones,t hus leading to the formation of sulfur-containing lactams.