Aldehydes and ketones were converted into 2-methylsulfinyl-5, 6-dihydro-4H-1, 3, 4- thiadiazines via the formation and base-induced ring-closure of N-alkylidene-N′-bis (alkylthio) methylenehydrazines followed by mCPBA oxidation. The subsequent Pummerer- type ring fission of the rings was performed by treating with trifluoroacetic anhydride or trifluoromethanesulfonic anhydride at− 78° C to give α, β-unsaturated esters and ketones ...
