Site-selective alkene borylation enabled by synergistic hydrometallation and borometallation

The selective installation of boryl units at less-activated sites, which will facilitate easy access to a range of core structures embedded within bioactive molecules, is a longstanding challenge. Here, we show that catalytic amounts of an earth-abundant Fe(ii)-based complex promote efficient borylations at typically less-reactive positions vicinal (β) to common functional units. Utility is highlighted through the synthesis of drug-like scaffolds and regioconvergent transformation of olefin feedstock to value-added products bearing Cβ–B stereogenic centres. These reactions proceed through tandem alkene isomerization followed by protoboration, and require that the in-situ-generated iron-hydride and iron-boryl catalysts function in synergy. By tuning the two processes of olefin transposition and protoboration, the present Fe-catalysed protocol can provide selective access to 1-boryl-, 2-boryl- or 3-borylalkane isomers. The insights gained from our studies are expected to advance general efforts towards unlocking selective functionalizations at other unactivated sites along the hydrocarbon chain. Site-selective functionalization at chemically inert positions within hydrocarbon molecules is a major challenge in organic chemistry. Iron-catalysed borylation at less-reactive positions vicinal to common functional units by sequential isomerization/protoboration of alkenes is reported.