Pd- and Cu-Cocatalyzed Anaerobic Olefin Aminoboration

The established conditions for the oxidative aminoboration of α-olefins employ O₂, a combustion accelerator, as the terminal oxidant. Herein, we report an efficient Pd- and Cu-cocatalyzed aminoboration of unactivated olefins, employing benzoquinone as the terminal oxidant. These conditions allow for enhanced turnover frequencies and an improved substrate scope relative to those of other Pd-catalyzed aminoboration reactions. These highly practical, selective, and high-yielding aminoboration conditions overcome many of the challenges associated with ligand-free oxidative Pd catalysis. The representative scope of the reaction includes 50 examples. α-Olefins, internal vinyl arenes, and strained cyclic olefins all participate along with a wide variety of amine nucleophiles. Mechanistic investigations support the idea that the rapid rate of oxidation by benzoquinone and Cu(II) prevents the aggregation of heterogeneous Pd(0) species, allowing the Pd to remain homogeneous throughout the aminoboration reaction. The scalability of the reaction and the synthetic utility of the products are demonstrated.