Iminium Carbonic Acid Derivative Salts. IX [1]. Synthesis of N,S-Containing Heterobicycles from N-Protected 2-Methylthio-1,3-thiazinium and 2-Methylthiothiazolium Salts Part 1. Preparation of N-Protected 2-Methylthio-1,3-thiazinium and 2-Methylthiothiazolium Salts and their Reaction with CH-Acidic Compounds

Article abstract of DOI:10.1002/jhet.5570330639

N-Boc-protected 1,3-thiazine-2-thiones and thiazolidin-2-thiones were transformed into the corresponding 2-methylthio-1,3-thiazinium and 2-methylthiothiazolium salts by methyl iodide or trimethyloxonium tetrafluoroborate. This activated species were reacted with CH-acidic compounds forming ketene-N,S-acetals. The protection group was removed with trifluoracetic acid to yield the N-unsubstituted ketene-N,S-acetals.