Abstract
Pyrolysis and photolysis of 2-amino-3,5-dicyano-6-phenyl-4H-pyran (1) afford HNCO, acrylonitrile, cinnamonitrile and 2-hydroxy-3,5-dicyano-6-phenylpyridine. Pyrolysis of 2-carboxyimino-3,5-dicyano-6-phenyl-4H-pyran (2) gives HCN, acrylonitrile, cinnamonitrile and 2-hydroxy-3,5-dicyano-6-phenylpyridine. Furthermore both pyrolysis and photolysis of 2,6-diamino-3,5-dicyanothiopyran (3) gives rise to HNCS, acrylonitrile and 6-amino-3,5-dicyano-6-mercaptopyridine. Moreover, comparative studies of pyrolysis, photolysis and mass spectra of 2,6-diamino-3,5-dicyano-4-arylthiopyran derivatives 4a-c revealed similar results as HNCS, cinnamonitrile derivatives and pyridinethione derivatives. The mass spectral fragmentation patterns of these compounds were recorded and studied to determine the homolysis fission involved in the rearrangements. Partial similarity of products obtained from pyrolysis and photolysis, and the mechanistic implications of these data are discussed.