title: Nickel-catalyzed cross-coupling of photoredox-generated radicals: uncovering a general manifold for stereoconvergence in nickel-catalyzed cross-couplings.
abstract: The cross-coupling of sp(3)-hybridized organoboron reagents via photoredox/nickel dual catalysis represents a new paradigm of reactivity for engaging alkylmetallic reagents in transition-metal-catalyzed processes. Reported here is an investigation into the mechanistic details of this important transformation using density functional theory. Calculations bring to light a new reaction pathway involving an alkylnickel(I) complex generated by addition of an alkyl radical to Ni(0) that is likely to operate simultaneously with the previously proposed mechanism. Analysis of the enantioselective variant of the transformation reveals an unexpected manifold for stereoinduction involving dynamic kinetic resolution (DKR) of a Ni(III) intermediate wherein the stereodetermining step is reductive elimination. Furthermore, calculations suggest that the DKR-based stereoinduction manifold may be responsible for stereoselectivity observed in numerous other stereoconvergent Ni-catalyzed cross-couplings and reductive couplings.
authors.affiliation: Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Osvaldo
authors.initials: O
authors.lastname: Gutierrez
authors.affiliation: Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
authors.forename: John C
authors.initials: JC
authors.lastname: Tellis
authors.affiliation: Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
authors.forename: David N
authors.initials: DN
authors.lastname: Primer
authors.affiliation: Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Molander
authors.affiliation: Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Marisa C
authors.initials: MC
authors.lastname: Kozlowski
mesh_terms: D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D007700:Kinetics; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D001896:Boron Compounds; D005609:Free Radicals; D009942:Organometallic Compounds; D009532:Nickel
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