In(OTf)3-catalysed easy access to dihydropyranocoumarin and dihydropyranochromone derivatives†
We developed an easy, In(OTf)3-catalysed, regioselective and generalizable method, for allylation/cyclization of β-ketolactone-type heterocyclic compounds. This reaction is proposed to proceed one-pot, through a Friedel–Crafts C-allylation followed by cyclization. This process represents a green synthetic method, as AcOH is the only isolated byproduct. We propose here, a protocol applicable for the construction of biologically active dihydropyranocoumarin and dihydropyranochromone derivatives.