5-PHENYLTETRAZOLE PHOTOCHEMISTRY . A NEW SOURCE OF PHENYLCARBENE

A product study of the photodecomposition of 5-phenyltetrazole (1) has been conducted. The results are compared with the corresponding thermolysis, and the photolysis of 5-phenyltetrazolide anion (7). Irradiation of 1 gives 1 equiv of nitrogen and a transient 1,3 dipolar intermediate. Dimerization of the latter to a dihydrotetrazine (2) comprises the major reaction path (>70%), but photolysis of 2 to benzonitrile and 3,5-diphenyl-1,2,4-triazole (4) also occurs. Though similar to thermolysis, the reaction is more selective. Photolysis of the anion (7) produces 2 equiv of nitrogen and products derived from the reaction of phenylcarbene with the solvent. Insertion (CH, OH, NH) and olefin addition products have been obtained. The method constitutes a new source of phenylcarbene, notable for its experimental simplicity. The reaction is believed to occur via phenyidiazomethane. © 1969, American Chemical Society. All rights reserved.