α‐Cyanothioacetamide and its derivatives in heterocyclic synthesis: Preparation of several new 4‐oxoquinazoline derivatives

The reaction of α-cyanothioacetamide (1) or its methylthio derivative (2) with anthranilic acid led to the formation of 3,4-dihydro-4-oxoquinazolin-2-yl acetonitrile (3). 3 condensed with aromatic aldehydes to give arylidene derivatives (4a-d) which could be prepared also via the reaction of 2-thiocarbamoylcinnamonitriles (5a-d) or their methylthio derivatives (6a-d) with anthranilic acid. 3 reacted with cinnamonitrile derivatives (7a-h) and (12a-d) to yield pyrido-[1,2-a]-quinazoline derivatives (10a-h) and (15a-d) which could also be prepared by the reaction of (4a-d) with malononitrile (11a), benzoyl acetonitrile (11b) and ethylcyanoacetate (16), respectively.