Alkaline earth metal catalyzed cascade, one-pot, solvent-free, and scalable synthesis of pyranocoumarins and benzo[b]pyrans

Ca(OTf)(2) catalyzed, cascade, one-pot, conjugate addition and annulation of various nucleophiles to the alpha,beta-unsaturated carbonyl compounds for the synthesis of biologically potent pyranocoumarins and benzo[b]pyrans has been illustrated. This one-pot, solvent-free, green-synthesis employs simple reaction conditions, with high yields and endures the substrate diversity. (C) 2015 Elsevier Ltd. All rights reserved.