Cascade Mn-Mediated γ-Alkylation/oxa-Michael Addition of Enones with 1,3-Dicarbonyls.

A radical-based strategy for regioselective γ-C-C bond formation/oxa-conjugate addition, forming the tetrahydrobenzofuran core common to many bioactive natural products is described. The technique utilizes readily available enone derivatives and 1,3-dicarbonyl compounds as coupling partners in an oxidative formal [3+2] cycloaddition mediated by Mn(III) . The transformation delivers polycyclic products in good yields and proceeds with complete regiocontrol and excellent stereoselectivity. Sterically encumbered substrates are notably well-tolerated and bond formation occurs readily to form neopentyl and all-carbon quaternary centers in good yields. Several stereo- and chemoselective transformations of the products are described.