Synthesis of novel heterocyclic fused 1,3-diazabuta-1,3-dienes and accompanying rearrangements in their cycloaddition reactions with ketenes: synthesis of heterocyclic fused pyrimidinone derivatives

The reactions of 1,3-diazabuta-1,3-dienes with 2-aminothiophenol have been shown to result in excellent yields of N-benzothiazol-2-yl-N′-aryl benzamidines . Their regioselective [4+2] cycloadditions with various ketenes are shown to yield novel benzothiazolo pyrimidinones . A similar and convenient protocol for the synthesis of bisthiosubstituted 1,3-diazabuta-1,3-dienes and and interesting rearrangements accompanying their [4+2] cycloadditions with a number of ketenes are described.