Congested C(sp³)-rich architectures enabled by iron-catalysed conjunctive alkylation

Catalytic cross-coupling by transition metals has revolutionized the formation of carbon–carbon bonds in organic synthesis. However, the challenge of forming multiple alkyl–alkyl bonds in crowded environments remains largely unresolved. Here we report the regioselective functionalization of olefins with sp³-hybridized organohalides and organozinc reagents using a simple (terpyridine)iron catalyst. Aliphatic groups of various sizes are successfully installed on either olefinic carbon, furnishing a diverse array of products with congested cores featuring carbon- or heteroatom-substituted stereocentres. The method enables access to valuable but synthetically challenging C(sp³)-rich molecules, including alicyclic compounds bearing multiple contiguous stereocentres, through annulation cascades. Mechanistic and theoretical studies suggest a stepwise iron-mediated radical carbometallation pathway followed by outer-sphere carbon–carbon bond formation, which potentially opens the door to a broader scope of transformations and new chemical space.