Si–B Functional Group Exchange Reaction Enabled by a Catalytic Amount of BH₃: Scope, Mechanism, and Application

Abstract

Functional group exchanges based on single-bond transformation are rare and challenging. In this regard, functional group exchange reactions of hydrosilanes proved to be more problematic. This is because this exchange requires the cleavage of the C–Si bond, while the Si–H bond is relatively easily activated for hydrosilanes. Herein, we report the first Si–B functional group exchange reactions of hydrosilanes with hydroboranes simply enabled by BH3 as a catalyst. Our methodology works for various aryl and alkyl hydrosilanes and different hydroboranes with the tolerance of general functional groups (up to 115 examples). Control experiments and density functional theory (DFT) studies reveal a distinct reaction pathway that involves consecutive C–Si/B–H and C–B/B–H σ-bond metathesis. Further investigations of using more readily available chlorosilanes, siloxane, fluorosilane, and silylborane for Si–B functional group exchanges, Ge–B functional group exchanges, and depolymerizative Si–B exchanges of polysilanes are also demonstrated. Moreover, the regeneration of MeSiH3 from polymethylhydrosiloxane (PMHS) is achieved. Notably, the formal hydrosilylation of a wide range of alkenes with SiH4 and MeSiH3 to selectively produce (chiral)­trihydrosilanes and (methyl)­dihydrosilanes is realized using inexpensive and readily available PhSiH3 and PhSiH2Me as gaseous SiH4 and MeSiH3 surrogates.

Aliphatic Hydrosilanes via Nickel-Catalyzed Reductive Csp3–Si Coupling of Primary Alkyl Bromides and Chlorohydrosilanes

“…Organohydrosilanes are vital synthetic precursors in producing functional organosilanes, and they play a significant role in various key research fields, including synthetic chemistry, materials science, and drug discovery . While there are several hydrosilanes (e.g., Ph 2 SiH 2 , PhSiH 3 , and Et 3 SiH) are commercially available, new synthetic methods for accessing hydrosilanes with improved molecular diversity and complexity are in high demand . In this context, the primary focus on producing aliphatic hydrosilanes has been the catalytic hydrosilylation of unsaturated compounds using R 2 SiH 2 and their surrogates, representing the current state-of-the-art (Scheme a, path a). , Despite formidable advances, these reactions often suffer from regioselectivity challenges.…”

Nickel-Catalyzed Metathesis between Carboxylic Acids and Thioesters: A Direct Access to Thioesters

“…In this area, recent advances in organic synthesis have been made for functional group metathesis, which involves the reversible cleavage of two single bonds to exchange two functional groups, a very promising strategy. Groundbreaking work has been accomplished recently by the Arndtsen, Morandi, Yamaguchi, and Wu groups (Scheme a). Despite these remarkable developments, exchanges based on single-bond transformation across functional groups were infrequent and remained difficult, which heavily depended on the establishment of an efficient catalytic system.…”