HETEROCYCLIC SYNTHESIS WITH ISOTHIOCYANATE AND SULFUR - A NOVEL ROUTEFOR THE SYNTHESIS OF PYRIDINO[2,3-D]THIAZOLE, THIAZOLO[4',5' 2,3] PYRIDINO[4,3-D]PYRIDAZINE AND THIAZOLO[4,5-B]ISOQUINOLINE DERIVATIVES/

The reaction of phenyl isothiocyanate and sulfur with the Knovenagel c ondensated adducts 1a-e afforded the pyridino[2,3-d]thiazole derivativ es 3a-e. The latter compounds proved to be versatile starting material s for the synthesis of polyfunctionally substituted thiazolo[4',5':2,3 ]pyridino[4,3-d]pyridazine and thiazolo[4,5-b]isoquinoline derivatives . Chemical and spectroscopic evidence for the structures of the new co mpounds, along with a sequence leading to their formation is described .