A Convenient Synthesis and Hepatoprotective Activity of Imidazo[1,2-c]pyrimido[5,4-e]pyrimidine, Tetraazaacenaphthene and Tetraazaphenalene from Cyclic Ketene Aminals Through Tandem Addition-Cyclization Reactions Original Research Article

A novel one-pot synthesis of imidazo[1,2-c]pyrimido[5,4-e]pyrimidinones (2), tetraazaacenaphthene-3,6-diones (4), tetarazaphenalene-1,7-dione (4d) is delineated from the reaction of cyclic ketene aminal (1) and alkyl or aryl isothiocyanate through tandem addition-cyclization reactions. However, reaction of ketene aminal (1a) with alkyl isothiocyanate only yielded angularly cyclized product 5 which did not react further to yield 6. The structure of 2c and 4d was ascertained by single crystal X-ray diffraction analysis which demonstrated a network of various inter- and intramolecular interactions, responsible for the stability and packing of the molecules in the crystalline state. Some of the compounds (2a–h) were screened for hepatoprotective activity but only 2a was found most effective.