2-bromo-2-nitropropane/zn promoted reductive cyclizations of ortho-carbonyl, imino, or azo substituted nitrobenzenes

Article abstract of DOI:10.3987/com-98-8349

Under the mild conditions, reductive cyclizations of 2-nitrobenzaldehydes, 2'-nitroacetophenone, and N-(2-nitrobenzylidene)anilines were accomplished in the presence of 2-bromo-2-nitropropane/Zn in methanolic solution. Under the similar conditions in MeOH/CH₂Cl₂, o-nitro-substituted phenylazobenzenes have been converted into 2-aryl-2H-benzotriazoles via reductive cyclizations that are widely used as UV absorbers. Synthesis and mechanistic details are discussed.