Thermolysis of N-arylnicotinamide oximes III

Thermolysis of N-arylnicotinamide oximes 1a-c (R =  H, CH3 and Cl) under nitrogen gives rise to benzimidazoles 3a-c as the major products (60-62%), in addition to nicotinonitrile 4, arylamines 5a-c, nicotinic acid 6, phenols 7a-c and 8a-c, nicotinanilides 9a-c, 2-(pyridin-3-yl) benzoxazoles 10a and carbazoles 11a-c. In the presence of naphthalene, thermolysis of 1a gave α- and β-naphthols 12 and 13 beside the previous products. Also pyrolysis of 1a in boiling tetralin lead to the formation of 1-hydroxytetralin 14, α-tetralone 15 and 1,1′-bitetralyl 16 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.