sp2−sp3 Hybridized Mixed Diboron: Synthesis, Characterization, and Copper-Catalyzed β-Boration of α,β-Unsaturated Conjugated Compounds

A novel sp(2)-sp(3) hybridized mixed diboron and its reactivity on the copper-catalyzed beta-boration of alpha,beta-unsaturated conjugated compounds to afford the corresponding beta-borated compounds is reported. The presence of sp(3)-hybridized boron provides a mild beta-boration condition in the absence of phosphine and base additives. Finally, our investigations demonstrate that the sp(2)-hybridized boron of the mixed diboron is selectively transferred to the beta-carbon of conjugated substrates.