One-pot approach to the synthesis of novel 12H-chromeno[2′,3′:4,5]imidazo[1,2-a]pyridines in aqueous media

The chromeno-imidazo[1,2-a]pyridine scaffold was generated in an one pot condensation/cyclization reaction involving a salicylaldehyde and 1-(cyanomethyl)pyridinium chloride, in aqueous sodium carbonate solution. These novel compounds were isolated in 47-71% yield. The reaction pathway was followed by H-1 NMR spectroscopy allowing a clear understanding of the side reactions involved in the process. Different mono-substituted pyridinium chlorides were synthesized and reacted with mono-substituted salicylaldehydes and a detailed discussion of the scope of the synthetic method is also presented. (C) 2010 Elsevier Ltd. All rights reserved.