Montmorillonite-KSF mediated one step synthesis of pyranochromene derivatives

Abstract

One-pot three-component reaction of substituted aromatic aldehydes, 2-cyanoacetamide and 4-hydroxycoumarin in the presence of Montmorillonite-KSF (MKSF) in ethanol results in the formation of pyrano[3,2-c]chromene-3-carboxylates (5a-m) has been described. The reaction was tested in different alcohols, afforded pyrano [3,2-c] chromene-3-carboxylates (5a-m) of the corresponding alcohols in good yield. The mechanism reveals that the alcohol (as solvent) plays a major role in the inter conversion of amide to the corresponding esters with Montmorillonite KSF (M-KSF) as a catalyst. Excellent yields, inexpensive and readily available substrates, environmentally benign reaction condition, shorter reaction time, and easy workup are the major advantageous features of this protocol.