Cu–N‐heterocyclic carbene‐catalysed synthesis of 2‐aryl‐3‐(arylethynyl)quinoxalines from one‐pot tandem coupling of o‐phenylenediamines and terminal alkynes

A series of new benzimidazolium chlorides bearing N,N '-benzyl, 2,4,6-trimethylbenzyl and 2,4,6-triisopropylbenzyl substituents have been designed and synthesized from various o-phenylenediamines. Subsequently, corresponding Cu-based N-heterocyclic carbenes (NHCs) were generated in situ in the reaction medium which represents a new application of NHCs exploiting distinct catalytic property towards intermolecular cyclization reaction cascade for the synthesis of 2-aryl-3-(arylethynyl)quinoxalines from o-phenylenediamines and terminal alkynes. The outcome of the cyclization reaction product depends upon the N,N '-substituents present on the benzimidazolium chlorides.