Photochemical reactions of azo compounds. V. Photochemical cyclodehydrogenations of Amino-, Acetyl-, and Nitro-azobenzenes

Abstract

4-Benzdaminoazobenzene and 4,4'-bisbenzalaminoazobenzene have been shown to undergo photochemical cyclodehydrogenation in concentrated (98%) sulphuric acid to give 2-aminobenzo[c]cinnoline and 2,9-diaminobenzo[c]cinnoline respectively in excellent yields; but 4-aminoazobenzene and 4,4'-diaminoazobenzene were not cyclized. 3-Arninoazobenzene and 3-benzalaminoazobenzene both gave 3-aminobenzo[c]cinnoline. 3-Nitro- and 3-acetyl-azobenzenes gave 3-nitro- and 3-acetyl-benzo[c]cinnolines; and 4-nitro- and 4-acetyl-azobenzenes gave 2-nitro- and 2-acetyl-benzo[c]cinnolines.