Nickel-catalyzed, silyl-directed, ortho-borylation of arenes via an unusual Ni(II)/Ni(IV) catalytic cycle.

Su, Xiaoshi; Li, Guoao; He, Linke; Chen, Shengda; Yang, Xiaoliang; Wang, Guoqiang; Li, Shuhua · Nat Commun · 2024

basic_science · Level V

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Abstract

Nickel-catalyzed C-H bond functionalization reactions provide an impressive alternative to those with noble metal catalysts due to their unique reactivity and low cost. However, the regioselective C(sp<sup>2</sup>)-H borylation reaction of arenes accomplished by nickel catalyst remains limited. We herein disclose a silyl-directed ortho C(sp<sup>2</sup>)-H borylation of substituted arenes with a Ni(cod)<sub>2</sub>/PMe<sub>3</sub>/KHMDS catalyst system. Using readily available starting materials, this protocol provides easy access to ortho-borylated benzylic hydrosilanes bearing flexible substitution patterns. These products can serve as versatile building blocks for the synthesis of sila or sila/borine heterocycles under mild conditions. Control experiments and DFT calculations suggest that a catalytic amount of base prompts the formation of Ni(II)-Bpin-ate complex, likely related to the C(sp<sup>2</sup>)-H bond activation. This borylation reaction might follow an unusual Ni(II)/Ni(IV) catalytic cycle.