Diboron-Enabled Nickel-Catalyzed Intermolecular Reductive Coupling of Styrenes With Aldehydes.

The direct reductive coupling of alkenes with aldehydes offers an attractive alternative to conventional carbonyl addition using preformed organometallic reagents, yet intermolecular coupling of simple alkenes remains challenging. In this study, we report a diboron-enabled nickel-catalyzed reductive coupling of styrenes and related alkenes with aliphatic aldehydes to afford saturated alcohols with up to 93% yield and high linear regioselectivity. A diboron reagent/lithium methoxide (MeOLi) combination is crucial for productive coupling and enables broad functional-group tolerance. Deuterium-labeling and control experiments indicate that ethanol is the predominant hydrogen source and are consistent with a nickelacycle-based reductive pathway. This reaction establishes a complementary nickel-catalyzed manifold for direct alkene-aldehyde reductive coupling under mild conditions.