Esterification and Chemoselective Synthesis of R-Tetrahydrothiazo-2-thione-4-carboxylic Esters Catalyzed by TiCl4

Abstract

A series of esters of R -tetrahydrothiazo-2-thione-4-carboxylic acid[ R -TTCA] was synthesized by direct esterification of R -TTCA with alcohols (CH 3 OH, C 2 H 5 OH, n -C 3 H 7 OH, i -C 3 H 7 OH, n -C 4 H 7 OH, sec-C 4 H 9 OH) in the presence of TiCl 4 as the catalyst at room temperature without using any other solvent or dehydrant in high yields, 91. 6%–99. 1% for primary alcohols and 55%–80% for secondary alcohols. The catalyst has a strong chemoselective activity for the esterification of primary alcohols with R -TTCA in the presence of secondary alcohols. Owing to high yield, high chemoselectivity, and mild conditions used, this is an efficient method for the esterification of primary alcohols with R -TTCA.