PYROLYSIS AND PHOTOLYSIS PROCESSES OF PYRAN AND THIOPYRAN DERIVATIVES

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-phenyI-4H- pyran (2) gives HCN, acrylonitrile, cinnamonitrile and 2-hydroxy-3,5-d icyano-6-phenylpyridine. Furthermore, both pyrolysis and photolysis of 2,6-diamino-3,5-dicyanothiopyran (3a) gives rise to HNCS, acrylonitri le and 6-amino-3,5-dicyano-6-mercaptopyridin, Moreover, comparative st udies of pyrolysis and photolysis of 2,6-dicyano-4-arylthiopyran deriv atives 3b-d revealed similar results. The similarity of products obtai ned from pyrolysis and photolysis and the mechanistic implications of these data are discussed.