Three thiirene 1-oxides 1, which possess bulky alkyl substituents at the 2- and 3-positions, afforded α-iminothio-ketones in 59–69% yields on successive treatment with trifluoroacetic anhydride and p-toluenesulfonamide, whereas 1 furnished oxazoles in 65–89% yields on the same treatment with trifluoroacetic anhydride and p-toluamide. A mechanism involving ring-expansion of the initial intermediates, sulfilimines, is proposed for these reactions.
dichloride (ClSCl) to give 2,3-dialkyl-2,3-dichlorothiiranes (2) nearly quantitatively. The alkaline hydrolysis of crude 2 resulted in the formation of thiirene 1-oxides (3) in 68–90% yields based on 1, thus providing a convenientsynthesis of 3.
providing the most convenient synthesis of thiirene 1-oxides. Disulfur dichloride also reacted with acetylenes to give 5 in good yields with the elimination of one sulfur atom. Although the alkalinehydrolysis of 5 provided 10 exclusively, acid hydrolysis gave a mixture of α-oxothioketone 9 and thiirene 1-oxide 10 in modest yields. All thiirene 1-oxides 10a–c isomerized to produce α-oxothioketones 9 in