Enantioselective Copper-Catalyzed Desymmetric Olefination via the Boron-Wittig Reaction

Boron-Wittig reactions represent one of the important tools for stereoselective synthesis of multisubstituted alkenes. However, using this strategy to build chiral frameworks is an extreme challenge. Here, we present an enantioselective boron-Wittig olefination of bis[(pinacol)boron]methane with biaryl dialdehydes. This protocol was facilitated by a Cu/SOP catalytic system and offered an efficient desymmetrization for the synthesis of axially chiral aryl alkenes. The good reactivity, outstanding selectivity (chem and enantio), broad substrate and functionality tolerance, and diverse product transformations ensured the potential broad applicability. The stereoselectivity of the reaction was intricately linked to a halogen ion, and a reasonable catalytic cycle was proposed.