Copper-Catalyzed C(sp(2))-H Difluoroalkylation of Aldehyde Derived Hydrazones with Diboron as Reductant.

An efficient and general method for C(sp(2))-H difluoroalkylation of aldehyde derived hydrazones via a Cu(II)/B2pin2-catalyzed reaction between difluoroalkyl bromides and hydrazones was developed. In this reaction, both aromatic and aliphatic difluoroalkylated aldehyde derived hydrazones could be achieved in good to excellent yields. For some heteroaromatic aldehyde derived hydrazones, two fluoroacetates could be introduced onto the final products. A preliminary mechanism study manifested that a difluoroalkyl radical via SET pathway was involved in the reaction. In addition, the catalytic diboron reagent plays an indispensable role in this transformation.