Regioselective [4+2] cycloaddition versus nucleophilic reactions of N-arylamino substituted 1,3-diaza-1,3-butadienes with ketenes: Synthesis of pyrimidinone and fused pyrimidinone derivatives .2.

A novel synthetic method for 3-aryl-6-phenyl-2-methylthio/secondaryamino substituted-4(3H)-pyrimidinones 5 and 9 by the reactions of N-arylamino substituted 1,3-diaza-1,3-butadienes 1 and 6 with phenyl-, vinyl-and isopropenylketenes is explored. Semi emperical AMI calculations on 1 and 6 are performed to explain the mechanism of their reaction with ketenes. Transformations of 5 and 9 leading to fused pyrimidinones 10 are also reported. (C) 1997 Elsevier Science Ltd.