GAS-PHASE STUDIES ON REDUCTIVE CYCLIZATION TO A BENZOTRIAZOLE DERIVATIVE FROM ITS PRECURSORS BY LIQUID-CHROMATOGRAPHY THERMABEAM TANDEM MASS-SPECTROMETRY

Liquid chromatography/Thermabeam mass spectrometry/mass spectrometry was carried out on the starting material, 2-nitro-2'hydroxy-5'-acetylazobenzene (1) and the intermediate N-oxide (2) formed by dithionite reduction of the starting material (1). The mass spectra of (1) and the intermediate (2) showed an abundant fragment ion that corresponds to that of 2-(2'-hydroxy-5'-acetylphenyl)benzotriazole (3). These results show that 3 could be formed from both 1 and 2. The formation of 3 in the gas phase is analogous to the chemical reduction processes of the 2-nitroazobenzene derivative 1 and the N-oxide 2 in solution.