Synthesis of novel tricyclic pyrimido[4,5-b][1,4]benzothiazepines via Bischler-Napieralski-type reactions

An efficient methodology for the synthesis of 4-phenylthiopyrimido[4,5-b][1,4]benzothiazepines was developed. This transformation can be rationalized by a mechanism similar to the Bischler-Napieralski-type reaction and the aryl sulfide group of the resulting 4-arylthiopyrimido[4,5-b][1,4]benzothiazepines can be subjected to selective oxidation and subsequent nucleophilic substitution.