Intramolecular Trapping of a Ketenimine Carbene Formed on Flash Vacuum Pyrolysis of 3-Phenylimino-3H-indazole and 3-Phenyliminoisobenzofuran-1-one

Abstract

Flash vacuum pyrolysis of 3-phenylimino-3H-indazole yielded biphenylene , benzonitrile and, by loss of dinitrogen followed by intramolecular trapping of a ketenimine carbene intermediate, the isomers fluorenimine , phenanthridine and 2-phenylbenzonitrile.Pyrolysis of 3-phenyliminoisobenzofuran-1-one gave the same five products together with N- phenylphthalimide . It is proposed that the same ketenimine carbene intermediate is involved in the two reactions. Pyrolysis of 3-o-tolylimino- and 3-benzylimino-isobenzofuran-1-one led to fragmentation without intramolecular trapping. Pyrolysis of 3-t-butyliminoisobenzofuran-1-one gave o-cyanobenzoic acid.