Synthesis of 1-Aryl-5-Nitrobenzotriazoles*

Abstract

3-Aryl-1-(3-nitrophenyl)triazenes were obtained in the cyclization reaction of diazotized 3-nitroaniline with arylamines in the presence of dimethyl sulfoxide and potassium carbonate to give 1-aryl- 5-nitrobenzotriazoles. Triazoles are commonly used intermediates in organic synthesis and have found application in industry, agriculture, and medicine (1). Many triazoles and their derivatives have high biological activity, including antitumor activity (2, 3). The synthesis of 1,2,3-benzotriazoles has been accomplished by various methods including diazotization of o-diaminoarenes, reaction of aryl azides with unsaturated compounds, and heterocyclization of o-amino-N-nitrosoarylamines or arylazobenzenes containing amino, nitro, or azido groups in the ortho position (4). The solid-phase synthesis of N-substituted 1H-benzotriazoles from ortho-halo- and ortho-nitroaryltriazenes has been described by Zimmermann and Brase (5). In the previous work (6), we developed a synthesis for triazoles using 9,10-anthraquinone derivatives. 3-Arylanthra(1,2-d)triazole-6,11-diones were obtained by the intramolecular heterocyclization of 1-aryl- 3-anthraquinonyltriazenes entailing intramolecular nucleophilic substitution of hydrogen in the presence of a basic catalyst. In the present work, we have studied the feasibility of forming the triazole ring using 1,3-diaryl- triazenes. We synthesized a series of 1,3-diaryltriazenes 1a-d containing a nitro group at position 3 in one of the aryl residues. The synthesis of diaryltriazenes was carried out by the diazotization of 3-nitroaniline and subsequent reaction of the resultant diazonium salt with a corresponding primary arylamine in pyridine. The composition and structure of the obtained diaryltriazenes were confirmed by physicochemical methods. The 1 H NMR spectra of diaryltriazenes 1b,c show a doubling of the signals both for the triazene and methyl group protons, indicating the existence of diphenyltriazenes containing an electron-withdrawing substituent and an electron-donor substituent in two tautomeric forms. The spectra of diaryltriazenes 1a,d, which combine a strong electron-withdrawing substituent and a weaker electron-withdrawing substituent, show