Synthesis of 5-phenyltetrazole and its N-methyl Derivatives in a Microreactor

Azidation of benzonitrile with dimethylammonium azide yielding 5-phenyltetrazole dimethylammonium salt was performed under microreactor conditions. The kinetics of azidation of benzonitrile in DMF was investigated at the range 80-95°C. The reaction rate constants were determined: [k.sup.11] x [10.sup.4] (L [mol.sup.-1] [s.sup.-1]): 0.79, 0.97, 1.19, 1.51, at 80, 85, 90, and 95°C, respectively. It was found that the reaction rate constants obtained in a microreactor are comparable to ones for a batch-type reactor. The thermodynamic parameters of azidation under the microreactor conditions correspond to the mechanism of the 1,3-dipolar cycloaddition of azides to nitriles. It was established that the excessive pressure in the microreactor notably accelerates the process. The alkylation of 5-phenyltetrazole with methyl iodide in microreactor was performed in dichloromethane-aqueous sodium hydroxide system. The accumulation of regioisomers of N1- and N2-methyl-5-phenyltetrazole in the microreactor under the conditions of slug flow of the reaction mixture occurs considerably faster than in the batch-type reactor in the conditions of phase-transfer catalysis. Key words: azidation of nitriles, tetrazoles, synthesis, alkylation, rate constants, microreactor