Enantioselective Copper-Catalyzed Methylboration of Alkenes

An enantioselective Cu-catalyzed borylative cross-coupling reaction of alkenes, bis­(pinacolato)­diboron (B₂(pin)₂), and methyl iodide is reported. Alkenes including styrenes, β-substituted styrenes, and challenging aliphatic olefins were smoothly transferred to the desired methylboration products with excellent diastereoselectivities (dr up to >99:1) and enantioselectivities (er up to 99:1). The utility of this process was demonstrated by the synthesis of naproxen and formal synthesis of two natural products.