An anomalous course of the condensation of 1,5-diaryl-3-formazyl glyoxylic acids with o-phenylenediamine. A simple synthesis of some benzimidazole-2-carboxamidarylhydrazones

Article abstract of DOI:10.1515/HC.2002.8.5.479

The condensation of 1,5-diaryl-3-formazylglyoxylic acids 1 with o-phenylenediamine did not afford 1,2-dihydro-3-(1,5-diaryl-3-formazyl)-chinoxalin-2-ones 2 as it had been described in a previous communication¹, but actually 1,5-diaryl-3-(2-benzimidazol-2-yl)-formazanes 7 with simultaneous elimination of formic acid. Also tetrazolium chlorides 3 and analogous picrates 4 described in the same communication¹ were not derivatives of 1,2-dihydro-quinoxaline-2-one, but in fact they were 2,3-diaryl-5-(benzimidazol-2-yl)-tetrazolium chlorides 8 and analogous picrates 9. Formazans 7 were transformed by reductive splitting into benzimidazol-2-carboxamid arylhydrazones 10.

Full text of DOI:10.1515/HC.2002.8.5.479

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