Ring Contraction of 2-Azidoquinoline and Quinoxaline 1-Oxides

Article abstract of DOI:10.1021/jo01314a020

Thermal ring contraction of 2-azidoquinoline 1-oxide with loss of nitrogen did not lead to the desired 2-cyano-1-hydroxyindole.Instead, 2-cyanoisatogen (9), 2,2'-dicyano-3,3'-bis (10), and 2-aminoquinoline 1-oxide (7) were formed.The mechanism is believed to involve an intermolecular addition to the intermediate cis-o-nitrosocinnamonitrile formed in a concerted ring-opening nitrogen loss, i.e., not involving a nitrene intermediate.In accord with this, both 2-azido-4-methylquinoline 1-oxide and 2-azidoquinoxaline 1-oxide give the expected 2-cyano-1-hydroxy-3-methylindole (18) and 2-cyano-1-hydroxybenzimidazole (26), respectively.