Iron-Catalyzed Reductive Cross-Coupling of Alkyl Electrophiles with Olefins

In terms of its abundance and its minimal toxicity, iron has advantages relative to other transition metals. Although alkyl-alkyl bond construction is central to organic synthesis, examples of iron-catalyzed alkyl-alkyl couplings of alkyl electrophiles are relatively sparse. Herein we report an iron catalyst that achieves cross-coupling reactions of alkyl electrophiles wherein olefins, in the presence of a hydrosilane, are used in place of alkylmetal reagents. Carbon-carbon bond formation proceeds at room temperature, and the method employs commercially available components (Fe(OAc)₂ , Xantphos, and Mg(OEt)₂ ); interestingly, this set of reagents can be applied directly to a distinct hydrofunctionalization of olefins, hydroboration. Mechanistic studies are consistent with the generation of an alkyl radical from the alkyl electrophile, as well as with reversibility for elementary steps that precede carbon-carbon bond formation (olefin binding to iron and β-migratory insertion).