CONVERSION OF -TRIFLUOROACETYL-5,6-DIHYDRO-4H-1,3,4-THIADIAZINES INTOALPHA,BETA-UNSATURATED ESTERS VIA CARBANION-INDUCED RING-OPENING AND DESULFURIZATION

A convenient conversion of 2-methylthio-5,6-dihydro-4H-1,3,4-thiadiazi nes 1 into alpha,beta-unsaturated esters was achieved through the proc edure including trifluoroacetylation of 1, carbanion-induced ring open ing of trifluoroacetamides 2, and reductive removal of heteroatom func tionality of the resulting S-alkenyl hydrazinecarbodithioates 3. Treat ment of 3 with a base under an aqueous condition also gave the corresp onding 6-alkylidene-4H-1,3,4-thiadiazin-5-ones 6.