Cobalt‐Catalyzed Regiodivergent Double Hydrosilylation of Arylacetylenes

Abstract

Double hydrosilylation of alkynes represents a straightforward method to synthesize bis(silane)s, yet it is challenging if α‐substituted vinylsilanes act as the intermediates. Here, a cobalt‐catalyzed regiodivergent double hydrosilylation of arylacetylenes is reported for the first time involving this challenge, accessing both vicinal and geminal bis(silane)s with exclusive regioselectivity. Various novel bis(silane)s containing Si−H bonds can be easily obtained. The gram‐scale reactions could be performed smoothly. Preliminarily mechanistic studies demonstrated that the reactions were initiated by cobalt‐catalyzed α‐hydrosilylation of alkynes, followed by cobalt‐catalyzed β‐hydrosilylation of the α‐vinylsilanes to deliver vicinal bis(silane)s, or hydride‐catalyzed α‐hydrosilylation to give geminal ones. Notably, these bis(silane)s can be used for the synthesis of high‐refractive‐index polymers (nd up to 1.83), demonstrating great potential utility in optical materials.

Co‐catalyzed Selective syn‐Hydrosilylation of Internal Alkynes

“…However, due to the low availability of noble metals and rising prices of such catalysts, more and more researchers try to develop sustainable alternatives. Thus, the complexes of Ni, [19–21] Mn,, [22] Fe, [23–26] and Co [26–46] were recently intensively studied. Interestingly, for Co‐catalyzed hydrosilylation of alkynes, the phenomenon of an extraordinary ligand control over the reaction pathway offers to receive all of the plausible regio‐ and/or stereoisomers, e. g ., β‐( E )‐, [26,41–44] β‐( Z )‐, [45] and α‐vinylsilanes [33,35–44] .…”

“…Given our recent success in incorporating readily available and cost‐effective cobalt complexes into organometallic synthesis, we hypothesized that an appropriate catalytic system could serve as a sustainable platform for producing diverse libraries of vinylsilanes [51–53] . Significantly, the subject of Co‐catalyzed hydrosilylation for internal alkynes, especially symmetrical ones, was limited to a few examples up until now [32,33,38–46] . As far as we know, only four research groups have reported satisfactory results to date, specifically regarding diaryl and bis‐aliphatic symmetrical internal alkynes [34–37,39,43] .…”

“…Thus, the complexes of Ni, [19–21] Mn,, [22] Fe, [23–26] and Co [26–46] were recently intensively studied. Interestingly, for Co‐catalyzed hydrosilylation of alkynes, the phenomenon of an extraordinary ligand control over the reaction pathway offers to receive all of the plausible regio‐ and/or stereoisomers, e. g ., β‐( E )‐, [26,41–44] β‐( Z )‐, [45] and α‐vinylsilanes [33,35–44] . However, to the best of our knowledge, there were no protocols describing the use of the triazine‐based PNP‐Co catalysts in the hydrosilylation of alkynes.…”

Hydrosilylation of Terminal Alkynes Catalyzed by an Air-Stable Manganese–NHC Complex

“…However, cobalt is the major player in this field, and many cobalt catalysts have been developed for the selective hydrosilylation of alkynes to give α-, β-( Z ), and β-( E )-isomers . Cobalt-catalyzed double hydrosilylation and sequential hydrosilylation/hydroboration are also reported. However, reports on manganese-catalyzed hydrosilylation of alkynes are very rare.…”

Organocalcium-Complex-Catalyzed Dehydrogenative Silylation and Mono/Dihydrosilylation Tandem Reactions of Terminal Alkynes

“…The scarcity of such a synthetic method is due to the difficulty of setting appropriate reaction conditions to perform intrinsically different styles of the two reactions. Furthermore, side reactions such as the hydrosilylation of terminal alkynes need to be avoided, , and the hydrosilylation of the resulting silylalkynes should be in good regioselectivity ( gem -disilylated alkenes vs 1,2-disilylated alkenes). Catalytic dehydrogenative silylation and dihydrosilylation tandem reactions of terminal alkynes with hydrosilanes provide gem -trisilylated alkanes.…”