An Efficient, One-Pot Regioselective Synthesis of Highly Functionalized Chromen-5-ones and Pyrano[3,2-c]chromen-5-ones via a Tandem Knoevenagel–Michael–Cyclization Sequence
facile, convenient, efficient, and high-yielding regioselective synthesis of a combinatorial library of hitherto unreported highly functionalized chromen-5-ones and pyrano[3,2-c]chromen-5-ones has been developed by one-potthree-component coupling of substituted aromatic aldehydes, dimedone/4-hydroxycoumarin with NMSM in the presence of catalytic amount of piperidine in ethanol medium. This transformation