Thermal fragmentation and rearrangement of some N-phenylbenzamide oxime dervatives II. Synthesis of benzimidazoles

Thermolysis of N-phenylbenzamide oximes I, II and III (R = Cl, NO₂ and OCH₃) under nitrogen gives rise to benzimidazoles as the major products (45-52%), in addition to benzonitrile, arylamines, benzoic acid, phenols, benzanilides, 2-phenyl benzoxazoles and carbazoles. In the presence of naphthalene, I gave α- and β-naphthols beside the previous products. Also heating of I under reflux boiling tetralin lead to the formation of 1-hydroxytetralin, α-tetralone and 1,1′-bitetralyl as the major products. The isolated products have been interpreted in the terms of a free radical mechanism involving the homolysis of N-O and/or C-N bonds.