Vicarious nucleophilic C-amination of nitrobenzene, 1-methyl-5-nitrobenzimidazole, and 1-methyl-6-nitrobenzimidazole in superbasic medium (potassium tert-butoxide-dimethyl sulfoxide) gave the corresponding amino-substituted derivatives. The yield of the amination product of 1-methyl-5-nitrobenzimidazole considerably increased in the presence of CuCl. ESR monitoring of these reactions revealed formation of primary radical anions from the substrates. Possible reaction mechanisms are discussed. VICARIOUS NUCLEOPHILIC C-AMINATION OF NITROBENZENE

The primary radical anions of substrate in the reactions of vicarious nucleophilic substitution of hydrogen in 1-methyl-4-nitropyrazole with 1,1,1-trimethylhydrazinium iodide and 4-amino-1,2,4-triazole in t-BuOK-DMSO were observed and identified by EPR monitoring. The probable mechanism of the substrate radical anions formation is discussed.

The constant attention of synthetic chemists to the vicarious nucleophilic substitution of hydrogen is reflected in a series of detailed reviews [1][2][3]. During the vicarious substitution of hydrogen an amino group is readily introduced into nitro aromatic and nitro heteroaromatic compounds [4,5], and this opens up broad synthetic possibilities (in particular the Sandmeyer reaction) and in itself explains the increased interest in the vicarious nucleophilic substitution of hydrogen. Interest has recently shifted to study of the mechanism of the process [6-9].Having put forward the idea of possible electron transfer during the vicarious nucleophilic substitution of hydrogen [9] and having confirmed this for the vicarious amination of nitrobenzene and a series of N-methylated nitroazoles [10-12], we assumed that the lower the reduction potential of the nitroazole the more readily the latter should undergo amination in the vicarious nucleophilic substitution of hydrogen. Our papers on the electrochemical reduction of azoles in an aprotic medium [13,14] show that their first reduction potentials decrease both with the accumulation of nitrogen atoms in the heterocycle and with the introduction of phenylene fragments. Apparently, overlap of the orbitals of the unshared electron pairs of adjacent pyridine nitrogen atoms or increase in the aromaticity of the system help to reduce the energy of the LUMO and facilitate the transfer of an electron to the molecule being reduced. _______ * Dedicated to Academician M. G. Voronkov on his 85th birthday. __________________________________________________________________________________________

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Amination O 0268Vicarious Nucleophilic C-Amination of Nitrobenzene and 5-and 6-Nitro-1-methylbenzimidazoles. -The title reaction in superbasic medium yields the corresponding amino-substituted derivatives. ESR monitoring reveals the formation of primary radical anions from the substrates. -(TITOVA, I. A.; VAKUL'SKAYA, T. I.; LARINA, L. I.; MIZANDRONTSEV, M. I.; VOLKOV, V. A.; DOLGUSHIN, G. V.; LOPYREV, V. A.; Russ.