Synthesis of 1,4-thiazino- and benzo-1,4-thiazinomorphinans: their acid-catalyzed rearrangement and study of the formation of unexpected oxidation products

Abstract The formation of 1,4-thiazine and benzo-1,4-thiazine rings was performed at the 6,7-positions of the morphinan backbone in order to synthesize systems annulated with a new six-membered ring providing potential pharmacological activity and the opportunity of easy functionalization. An unexpected oxidation of cyclic sulfur was observed in both cases affording either sulfones or open-ringed bis-morphinan-type by-product. These phenomena are in conformity with the observations and mechanistic explanations made by several research groups in the past in connection with the photosensitized oxidation of cyclic sulfides.