Sequential Ugi/Strecker reactions via microwave assisted organic synthesis: novel 3-center-4-component and 3-center-5-component multi-component reactions

Two novel one-step microwave mediated syntheses of arrays of 3-iminoaryl-imidazo[1,2-a]pyridines and imidazo[1,2-a]pyridyn-3-ylamino-2-acetonitriles are reported. Reactions are performed under microwave condition in methanol by simply mixing alpha-amino-pyridines, aldehydes, and trimethylsilylcyanide (TMSCN) with distinct reagent stoichiometries, catalyzed by polymer-bound scandium triflate, to afford either product. Furthermore, functionally different aldehydes were shown to proceed to different end-points, adding an extra caveat to the studies. The new methodology represents examples of both formal 3-center-4-component and 3-center-5-component multi-component reactions. (c) 2006 Elsevier Ltd. All rights reserved.