Expeditious Synthesis of Imidazole- and Pyrrole-Fused Benzodiazocines

Abstract

A straightforward strategy for the synthesis of imidazole fused-benzodiazocine from 1-(2-nitrophenyl)-1H-imidazole-2-carbaldehyde via Morita-Baylis-Hillman reaction followed by reductive intramolecular cyclization is described. Alternatively the Horner-Wadsworth-Emmons reaction of this substrate with triethyl phosphonoacetate yielded (E)-ethyl 3-(1-(2-nitrophenyl)-1H-imidazol-2-yl) acrylate which upon sequential reduction, saponification and amide coupling furnished imidazole-fused- diazocinones. On the other hand 1-(2-nitrophenyl)-1H-pyrrole-2-carbaldehyde failed to undergo the Morita-Baylis-Hillman reaction but successfully yields (E)-ethyl 3-(1-(2-nitrophenyl)-1H-pyrrol-2-yl)acrylate via Horner-Wadsworth-Emmons reaction which through a similar series of reaction as for imidazole produced pyrrole-fused-diazocinone in good yields.