Thermal and photofragmentation of N-benzoylhydrazone derivatives

Two selected benzoylhydrazones I and II were subjected to thermolysis by re flux at 200 degrees C. Benzil, benzoic acid, biphenyl, benzanilide together with the corresponding ketones, nitriles and imines were isolated. Similar treatment of the third hydrazone III at 250 degrees C afforded, in additio n to the previous products, bibenzyl, stilbene, and 2-phenylindole. Photoly sis of the same hydrazones I-III in acetonitrile gave the previously report ed products but in different ratios along with azine derivatives and substi tuted methanes. A free radical mechanism involving homolysis of the N-N and C-N bonds is suggested, substantiated by trapping of phenyl radical with i soquinoline, to account for the formation of the identified products.