An unexpected p-Toluenesulfonic acid catalyzed 1,3-migration of thiocarbonyl: Selective formation of 1,3-dioxolane-2-thione ring and optimization study

Abstract

The selective opening of 5, 6-O-acetal of 3-O-(1,2: 5,6-di -O-i sopropylidine-α-D-gl ucofuranose)-1H-benzo [d][1,2,3]triazole-1-carbothioate (3) afforded bis(1,2-O-isopropylidene-5,6-thionocarbonato-α-D-glucofuranose (5) as a sole crystalline product. The reaction involved the treatment of 3 with p-toluenesulfonic acid in CH2 Cl2 at ambient temperature for 12 h giving compound 5 in 96% yield via 1,3-migration of thiocarbonyl moiety. The optimization study further revealed that the five membered dioxolane-2-thione ring was stabilized over six member ring by 8.78 kcal/mol.