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

reaction: see text] Novel tricyclic pyrimido4,5-b]1,4]benzothiazepines were readily prepared from 5-amino-4,6-bis(arylthio)pyrimidines and carboxylic acids via Bischler-Napieralski-type reactions. The 6-aryl sulfide group of the resulting pyrimido4,5-b]1,4]benzothiazepines could be selectively oxidized to its corresponding sulfoxide, which underwent facile substitution reactions when treated with nucleophiles such as an amine. This synthetic strategy provides an efficient way to access a library of novel heterocyclic compounds that are of interest in drug discovery.