Photoredox Activation of Inert Alkyl Chlorides for the Reductive Cross-Coupling with Aromatic Alkenes.

Abstract

The inertness of chloroalkanes has precluded them as coupling partners for cross-coupling reactions. Herein we disclose a general strategy for the activation of inert alkyl chlorides through photoredox catalysis and their use as coupling partners with alkenes. The catalytic system is formed by [Ni(OTf)(Py2 Ts tacn)](OTf) (1Ni ), which is responsible for the Csp3 -Cl bond activation, and [Ir(NMe2 bpy)(ppy)2 ]PF6, (PCIr NMe2 ), which is the photoredox catalyst. Combined experimental and theoretical studies show an in situ photogenerated NiI intermediate ([Ni(Py2 Ts tacn)]+ ) which is catalytically competent for the Csp3 -Cl bond cleavage via a SN 2 mechanism for primary alkyl chlorides, forming carbon-centered free radicals, which react with the olefin leading to the formation of the Csp3 -Csp3 bond. These results suggest inert alkyl chlorides can be electrophiles for developing new intermolecular strategies in which low-valent aminopyridine nickel complexes act as key catalytic species.