Pyrrole studies part 47. C NMR Spectroscopic characterisation of the products of the reaction of formylpyrroles with aniline and diaminobenzenes

Abstract

Pyrrole-3, 4-dicarboxaldehydes react with aniline to produce" bis-imines" having a 3H-pyrrole structure, 3b. In contrast, pyrrole-2-carboxaldehyde and pyrrole-2, 5-dicarboxaldehydes produce 1H-pyrrolylmethylenimines. Benzimidazolyl derivatives, are formed exclusively from the reaction of β-formylpyrroles with 1, 2-diaminobenzene, while α-formylpyrroles form 2: 1 bisimines or benzimidazoles depending upon the reaction conditions. Pyrrole-2, 4-dicarboxaldehydes react with aniline preferentially at the 4-CHO group. With an excess of aniline, the bis-imine is produced.