New Routes to 1,2-Diazoles With a Fused Ring System by Reductive and Oxidative Cyclizations

Heating aromatic or heteroaromatic compounds carrying a carbonyl and an arylazo group at adjacent nuclear positions with triethyl phosphite resulted in the formation of a 1,2-diazole ring through reductive cyclizations. Similar, but oxidative, cyclizations were effected by the action of selenium dioxide on compounds with a methylene group at an appropriate position.