Highly Linear Selective Cobalt-Catalyzed Addition of Aryl Imines to Styrenes: Reversing Intrinsic Regioselectivity by Ligand Elaboration

Highly linear selective, imine‐directed hydroarylation of styrene has been achieved with cobalt‐based catalytic systems featuring bis(2,4‐dimethoxyphenyl)(phenyl)phosphine and either 2‐methoxypyridine or DBU as a ligand and a Lewis base additive, respectively, thus affording a variety of 1,2‐diarylethanes (bibenzyls) in good yields under mild reaction conditions. The triarylphosphine controls the regioselectivity, while the Lewis base significantly accelerates the reaction. Ligand screening and deuterium‐labeling studies provide implications about the roles of the ligand and the Lewis base in the crucial CC reductive elimination step. Paired off: The title reaction has been achieved with cobalt‐based catalytic systems featuring bis(2,4‐dimethoxyphenyl)(phenyl)phosphine (L) and either 2‐methoxypyridine or DBU (LB), thus affording a variety of 1,2‐diarylethanes in good yields. Ligand screening and deuterium‐labeling studies show the ligand and Lewis base to be important in the crucial CC reductive elimination step. Cy=cyclohexyl, PMP=para‐methoxyphenyl.