Regioselective Annulation of Seven-, Eight-, and Nine-Membered Azaheterocycles to Benzimidazole Starting from Chloro-Substituted 2-Aza-1,3-dienes

Abstract

Readily available 1-aryl-1,3,4,4-tetrachloro-2-azabuta-1,3-dienes enter into a pronouncedly directed cyclocondensation reaction with 2-(ω-aminoalkyl)benzimidazoles to give the corresponding seven-, eight-, and nine-membered azaheterocycles regioselectively annulated to the benzimidazole nucleus. The products thus obtained are derived from benzimidazole fused to 2H-1,3,5-triazepine, 1,3,5-triazocine, or 2H-1,3,5-triazonine, in accordance with comprehensive structural determination by spectroscopic methods and X-ray diffraction analysis.