Iron-Catalyzed Regioselective Alkenylboration of Olefins

The first examples of an iron-catalyzed three-component synthesis of homoallylic boronates from regioselective union of bis(pinacolato)diboron, an alkenyl halide (bromide, chloride or fluoride), and an olefin are disclosed. Products that bear tertiary or quaternary carbon centers could be generated in up to 87 % yield as single regioisomers with complete retention of the olefin stereochemistry. With cyclopropylidene-containing substrates, ring cleavage leading to trisubstituted E-alkenylboronates were selectively obtained. Mechanistic studies revealed reaction attributes that are distinct from previously reported alkene carboboration pathways.

Automated summary

A novel iron-catalyzed three-component synthesis method has been developed for the regioselective union of bis(pinacolato)diboron, an alkenyl halide, and an olefin to produce homoallylic boronates. The reaction can generate products with tertiary or quaternary carbon centers in up to 87% yield as single regioisomers with complete retention of the olefin stereochemistry. Selective formation of trisubstituted E-alkenylboronates from cyclopropylidene-containing substrates was also observed, revealing unique reaction attributes distinct from previously reported pathways.