Copper-catalyzed persulfate oxidation of δ-lactones to tetrahydrofurans with one-carbon deletion

Synthesis of 2-aryl tetrahydrofurans from 2-aryl-δ-lactones with one-carbon deletion was established by using a catalytic amount (10 mol%) of CuSO4 and two equivalents of sodium persulfate in 5% sulfuric acid. Copper(III) or sulfate radical anion worked as oxidant to generate carboxy radicals and α-aryl carbocations. The aryl group stabilized radicals formed by decarboxylation of the carboxy radicals.