An Expedient Route to Dihydrothiazines, a Virtually Unknown Class of Heterocycles

Upon heating at 180-200 degrees C in diphenyl ether, S-(4-oximinoalkyl)xanthates with a secondary isopropyl or isobutyl group on the oxygen undergo a Chugaev elimination followed by ring closure onto the oxime to give dihydrothiazines, a virtually unknown class of heterocycles.