Copper(I)-Catalyzed Direct Oxidative Annulation of 1,3-Dicarbonyl Compounds with Maleimides: Access to Polysubstituted Dihydrofuran Derivatives.

An efficient annulation method for the synthesis of polysubstituted dihydrofurans from 1,3-dicarbonyl compounds and maleimides is described. The reactions can afford furo[2,3-]pyrrole derivatives with satisfactory yields. The developed strategy realizes the direct oxidative double C(sp)-H functionalization in the presence of copper(I) salts and 2-(-butylperoxy)-2-methylpropane. Meanwhile, this protocol features a mild reaction condition and simple catalytic system. A reaction mechanism involving a single electron oxidation is also proposed.