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The base-promoted homolytic cross-coupling reaction of nitroarenes and anilines involving single electron transfer and leading to benzo[ c]cinnoline oxides reported by Sythana et al. (S. K. Sythana, S. Unni, Y. M. Kshirsagar, P. R. Bhagat, Eur. J. Org. Chem. 2014, 311) was shown to be incorrect. In fact, nucleophilic substitution of hydrogen with anilide anions takes place, which leads to the formation of intermediate N-aryl-2-nitrosoanilines followed by base-promoted cyclization to phenazines and/or their N-oxide derivatives. Three of the phenazine N-oxides, which were erroneously described as benzo[ c]cinnoline oxides by Sythana et al., were obtained independently in the cyclization of N-aryl-2-nitrosoanilines possessing a leaving group at the ortho position in the N-aryl ring. A competitive substitution of hydrogen and a leaving group lead to the formation of 1-substituted phenazines and phenazine N-oxides, respectively, depending on the reaction conditions and the leaving group. [ABSTRACT FROM AUTHOR]

N-Aryl-substituted 2-nitrosoanilines (=2-nitrosobenzenamines) 1, readily available by nucleophilic substitution of the ortho-H-atom in nitroarenes with arenamines, react with 2-substituted acetic acid esters in the presence of a weak base giving 1-arylquinoxalin-2(1 H)-ones ( Scheme 2). This cyclocondensation allows for the synthesis of compounds 2- 4, unsubstituted at C(3) or substituted by alkyl, aryl, ester, amide, and keto groups, in good to excellent yields ( Tables 1- 4). [ABSTRACT FROM AUTHOR]

Aromatic nucleophilic substitution of halogens in N-aryl-2-nitrosoanilines with ammonia, alkylamines and alkoxide ions proceeds efficiently and highly regioselectively in the position para to the nitroso group. When two halogen atoms ortho and para are present, the latter is substituted exclusively. Oxidative substitu-tion of hydrogen at the unsubstituted ortho position of the nitro-soaniline ring does not compete with substitution of para halogen atoms. The reaction allows the synthesis of N-aryl-2-nitrosoanilines which cannot be obtained according to known methods. [ABSTRACT FROM AUTHOR]