A PUMMERER-TYPE NOVEL RING FISSION OF 2-METHYLSULFINYL-5,6-DIHYDRO-4H-1,3,4-THIADIAZINE DERIVATIVES - A HOMOLOGATION OF ALDEHYDES AND KETONES

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 mCPB A oxidation. The subsequent Pummerer-type ring fission of the rings wa s performed by treating with trifluoroacetic anhydride or trifluoromet hanesulfonic anhydride at -78 degrees C to give alpha,beta-unsaturated esters and ketones in modest yields. Thus, this reaction sequence was regarded as being a new method for the two-carbon homologation of ald ehydes and ketones.