Electrochemical cyclization of 1-phenyl-2(-1′chlorophenyl)-substituted five-membered nitrogen heterocycles. Application to the synthesis of phenanthridines

Abstract

Pyrrolo[1,2-f]phenanthridine (compound 4), 3-phenylimidazo[1,2-f]phenanthridine 8, tetrazolo[1,5-f]phenanthridine 11 and benzo[c]tetrazolo[1,5-f]phenanthridine 12 have been prepared using an electrochemical cyclization procedure. Treatment of the imidazophenanthridine with singlet oxygen yields a phenanthridone by degradation of the heterocyclic system. Lithium aluminium hydride reduction of the tetrazolophenanthridines yields the phenanthridine.