Copper-Catalyzed Cross-Coupling of Silicon Pronucleophiles with Unactivated Alkyl Electrophiles Coupled with Radical Cyclization

A copper-catalyzed C(sp³)-Si cross-coupling of aliphatic C(sp³)-I electrophiles using a Si-B reagent as the silicon pronucleophile is reported. The reaction involves an alkyl radical intermediate that also engages in 5-exo-trig ring closures onto pendant alkenes prior to the terminating C(sp³)-Si bond formation. Several Ueno-Stork-type precursors cyclized with excellent diastereocontrol in good yields. The base-mediated release of the silicon nucleophile and the copper-catalyzed radical process are analyzed by quantum-chemical calculations, leading to a full mechanistic picture.