Highly tunable multi-borylation of gem-difluoroalkenes via copper catalysis

Multi-borylated compounds are useful starting materials for the construction of complex molecules. Although certain classes of multi-borylated compounds, such as geminal and 1,2-bis(boronates), can now be accessed selectively by several well-established methods, the synthesis of one class—those containing more than two boronate substituents—remains a great challenge. Here, copper catalytic systems were developed for the borylation of gem-difluoroalkenes with B2pin2 via dual C–F bond activation to afford multi-borylate libraries—1,2-alkyldiboronates, 1,1,2-alkyltriboronates and 1,1,1,2-alkyltetraboronates—by slightly tuning the reaction conditions. The advantages of this strategy include not only avoiding the use of different methods and substrates for each type of multi-substituted alkyl boronate, but also the excellent functional group compatibility, readily accessible gem-difluorovinyl group and highly chemoselective process. Organoboron compounds are versatile intermediates in organic chemistry, and as such the selective introduction of multiple boron-containing groups is of high interest. Here Shi and co-workers report a copper-catalysed method that can selectively introduce two, three or four boronate groups into common starting materials by simply making minor modifications to the reaction conditions.