Acid-Mediated Highly Regioselective Oxidation of Substituted Furans: A Simple and Direct Entry to Substituted Butenolides

The scope and limitations of an expeditious synthesis of substituted butenolides from 3-substituted or 3,4-disubstituted furans is described. The entire process embodies a controlled oxidation of the furan core to a 2,5dialkoxy-dihydrofuran intermediate and a regioselective acid-catalyzed hydrolysis to the butenolide derivative. 3-Substituted furans yield exclusively 2-substituted butenolides. Calculations studies provide substantiation of a proposed mechanism.