Nickel-Catalyzed Mono- and Dihydrosilylation of Aliphatic Alkynes in Aqueous and Aerobic Conditions

Abstract

1,1-Disilanes are synthetically versatile building blocks, owing to their low toxicity, high stability, and unique structures. However, the practical synthesis of 1,1-disilanes is still a challenge. Despite the available Fe-, Co-, La-, and B-catalyzed protocols, the use of highly reactive reductants, such as EtMgBr, NaBHEt3, or KHMDS, inevitably requires air- and moisture-free conditions. Herein, we report the homogeneous Ni-catalyzed mono- and dihydrosilylation of aliphatic terminal alkynes under either air and water conditions or neat conditions, affording β-(E)-vinylsilanes and 1,1-disilanes in high yields with complete regioselectivity and stereoselectivity. Importantly, our method is gram-scalable and the sole example of Ni-catalyzed dihydrosilylation of alkynes. We demonstrated the introduction of different silyl groups through the stepwise addition of each silane source in a reaction vessel. Furthermore, the reaction intermediates were characterized with spectroscopic/spectrometric tools, and density functional theory calculations were performed to understand the reaction mechanism and the origins of the regioselectivity for β-(E)-vinylsilanes and 1,1-disilanes.

Copper-Catalyzed Formal Dihydrosilylation of Terminal Alkynes: A C(sp)–H Silylation-Hydrosilylation-Hydrogenation Sequence

“…Considering that arylacetylenes do not undergo the iron- and cobalt-catalyzed dihydrosilylation of alkynes, − we chose the reaction between phenylacetylene 1a and PhSiH 3 to identify copper catalysts and reaction conditions for the copper-catalyzed dihydrosilylation of alkynes. The copper catalysts employed in this study were generated in situ from CuOAc and bisphosphines and were activated by the reaction with PhSiH 3 .…”

“…Alkynes are versatile and readily accessible reagents for organic synthesis, and catalytic hydrosilylation of alkynes has been extensively explored with various transition metal catalysts to prepare structurally diverse vinylsilanes with precise control over regio- and stereoselectivity (Figure A). − In principle, transition metal-catalyzed sequential dihydrosilylation of alkynes provides the most straightforward and atom-efficient approach to accessing disilylalkanes, provided that this dihydrosilylation process occurs with high selectivity (Figure B). − Accordingly, iron, cobalt, and nickel compounds have been reported to catalyze dihydrosilylation of terminal alkynes to afford gem -disilylalkane products (Figure C). − However, these iron-, cobalt-, and nickel-catalyzed dihydrosilylation reactions proceeded only with alkyl-substituted alkynes. When aryl-substituted alkynes reacted with hydrosilanes in the presence of the identified iron and cobalt catalysts, the reactions stopped at the stage of monohydrosilylation, yielding only ( E )-vinylsilane products.…”

“…The scope of alkynes for copper-catalyzed dihydrosilylation covers both alkyl- and arylacetylenes. Different from iron-, cobalt-, and nickel-catalyzed dihydrosilylation reactions, − this copper-catalyzed dihydrosilylation reaction occurs through a new pathway combining copper-catalyzed C­(sp)–H silylation of terminal alkynes to generate alkynylsilanes, hydrosilylation of alkynylsilanes to produce gem -disilylalkenes, and hydrogenation of gem -disilylalkenes to afford gem -disilylalkane products.…”

Recent advances in earth-abundant transition metal-catalyzed dihydrosilylation of terminal alkynes

“…Nonetheless, Ni-catalyzed hydrosilylation of alkynes is relatively rare, and the few reported examples of monohydrosilylation reactions are mainly based on the use of a porous organic polymer (POP) as a heterogeneous ligand ( Zhou et al, 2018 ). Very recently, Jung and co-workers reported a Ni-catalyzed protocol for dihydrosilylation of alkynes, a highly practical method that circumvents the need of strong reductants while being operative even under aqueous and aerobic conditions ( Lee et al, 2024 ). The reaction was found to be highly effective using Ni(acac) 2 as a precatalyst, 2,9-dimethyl-1,10-phenanthroline ligand L1 , Ph 2 SiH 2 as the sole silane source, and H 2 O solvent at 30°C, resulting in the formation of 1,1-disilylalkanes 13 with excellent regioselectivity ( Scheme 7A ).…”