Abstract:A metal‐free, intermolecular syn‐addition of hexamethyldisilane across simple alkenes is reported. The catalytic cycle is initiated and propagated by the transfer of a methyl group from the disilane to a silylium‐ion‐like intermediate, corresponding to the (re)generation of the silylium‐ion catalyst. The key feature of the reaction sequence is the cleavage of the Si−Si bond in a 1,3‐silyl shift from silicon to carbon. A central intermediate of the catalysis was structurally characterized by X‐ray diffraction, … Show more
“…2 silylium catalysis; however, the reaction scope is currently limited to the installation of TMS groups using TMS-TMS. 18 A combination of TBAClO4 as the electrolyte, a magnesium sacrificial anode, and a graphite cathode provided the optimal 94% yield under a constant current of 10 mA (cathodic potential ~ -0.85 V vs. Mg 0/2+ ). Notably, even TMSOAc with a very strong Si-O bond (120-140 kcal/mol) can be activated, resulting in 31% yield.…”
“…Several electron-deficient and electron-rich heterocycles (10)(11) and ferrocene (12) were also compatible with the reaction conditions. We also investigated other types of π-systems such as allenes (15), internal alkynes (16), conjugated dienes (17), and enynes (18) to generate a range of allyl and vinyl silanes, which could be further derivatized using cross-coupling and allylation reactions. Moreover, vinyl boronates proved to be suitable substrates, providing products (19-23) with gem-(B,Si) substitution, which are versatile functional groups in organic synthesis.…”
Section: Scheme 2 Electroreductive Disilylation Of Alkenesmentioning
The construction of C(sp<sup>3</sup>)–Si bonds is important in synthetic, medicinal, and materials chemistry. In this context, reactions mediated by silyl radicals have become increasingly attractive but methods for accessing these intermediates remain limited. We present a new strategy for silyl radical generation via electroreduction of readily available chlorosilanes. At highly biased potentials, electrochemistry grants access to silyl radicals through energetically uphill reductive cleavage of strong Si–Cl bonds. This strategy proved to be general in various alkene silylation reactions including disilylation, hydrosilylation, and allylic silylation under simple and transition-metal-free conditions.
“…2 silylium catalysis; however, the reaction scope is currently limited to the installation of TMS groups using TMS-TMS. 18 A combination of TBAClO4 as the electrolyte, a magnesium sacrificial anode, and a graphite cathode provided the optimal 94% yield under a constant current of 10 mA (cathodic potential ~ -0.85 V vs. Mg 0/2+ ). Notably, even TMSOAc with a very strong Si-O bond (120-140 kcal/mol) can be activated, resulting in 31% yield.…”
“…Several electron-deficient and electron-rich heterocycles (10)(11) and ferrocene (12) were also compatible with the reaction conditions. We also investigated other types of π-systems such as allenes (15), internal alkynes (16), conjugated dienes (17), and enynes (18) to generate a range of allyl and vinyl silanes, which could be further derivatized using cross-coupling and allylation reactions. Moreover, vinyl boronates proved to be suitable substrates, providing products (19-23) with gem-(B,Si) substitution, which are versatile functional groups in organic synthesis.…”
Section: Scheme 2 Electroreductive Disilylation Of Alkenesmentioning
The construction of C(sp<sup>3</sup>)–Si bonds is important in synthetic, medicinal, and materials chemistry. In this context, reactions mediated by silyl radicals have become increasingly attractive but methods for accessing these intermediates remain limited. We present a new strategy for silyl radical generation via electroreduction of readily available chlorosilanes. At highly biased potentials, electrochemistry grants access to silyl radicals through energetically uphill reductive cleavage of strong Si–Cl bonds. This strategy proved to be general in various alkene silylation reactions including disilylation, hydrosilylation, and allylic silylation under simple and transition-metal-free conditions.
“…Several electron-deficient and electron-rich heterocycles (10-11) and ferrocene (12) were also compatible with the reaction conditions. We also investigated other types of π-systems such as allenes (15), internal alkynes (16), conjugated dienes (17), and enynes (18) to generate a range of allyl and vinyl silanes, which could be further derivatized using cross-coupling and allylation reactions. Moreover, vinyl boronates proved to be suitable substrates, providing products (19-23) with gem-(B,Si) substitution, which are versatile functional groups in organic synthesis.…”
Section: Scheme 2 Electroreductive Disilylation Of Alkenesmentioning
confidence: 99%
“…Oesterich reported an elegant example of alkene disilylation via silylium catalysis; however, the reaction scope is currently limited to the installation of TMS groups using TMS-TMS. 17 A combination of TBAClO4 as the electrolyte, a magnesium sacrificial anode, and a graphite cathode provided the optimal 94% yield under a constant current of 10 mA (cathodic potential ~ -0.85 V vs. Mg 0/2+ ). Notably, even TMSOAc with a very strong Si-O bond (120-140 kcal/mol) can be activated, resulting in 31% yield.…”
The construction of C(sp<sup>3</sup>)–Si bonds is important in synthetic, medicinal, and materials chemistry. In this context, reactions mediated by silyl radicals have become increasingly attractive but methods for accessing these intermediates remain limited. We present a new strategy for silyl radical generation via electroreduction of readily available chlorosilanes. At highly biased potentials, electrochemistry grants access to silyl radicals through energetically uphill reductive cleavage of strong Si–Cl bonds. This strategy proved to be general in various alkene silylation reactions including disilylation, hydrosilylation, and allylic silylation under simple and transition-metal-free conditions.
“…1a ) 13 – 17 . Despite significant advances in this reaction, there are still some limitations: (1) symmetric disilanes are frequently employed in most reactions to assemble two identical silyl groups on olefinic products, but are difficult to differentiate chemoselectively for stepwise downstream transformations 18 – 25 ; (2) the main catalysts are low-valent platinum group transition metal complexes, which are expensive; and (3) internal alkynes remain challenging substrates with low inherent reactivity in most catalytic systems. Fig.…”
Abstract1,2-Bis-silyl alkenes have exciting synthetic potential for programmable sequential synthesis via manipulation of the two vicinal silyl groups. Transition metal-catalyzed bis-silylation of alkynes with disilanes is the most straightforward strategy to access such useful building blocks. However, this process has some limitations: (1) symmetric disilanes are frequently employed in most of the reactions to assemble two identical silyl groups, which makes chemoselective differentiation for stepwise downstream transformations difficult; (2) the main catalysts are low-valent platinum group transition metal complexes, which are expensive; and (3) internal alkynes remain challenging substrates with low inherent reactivity. Thus, the development of abundant metal-catalyzed bis-silylation of internal alkynes with unsymmetrical disilanes is of significance. Herein, we solve most of the aforementioned limitations in bis-silylation of unsaturated bonds by developing a strongly coordinating disilane reagent and a Ni(0) catalytic system. Importantly, we sufficiently realize the stepwise recognition of the two silyl groups, making this synthetic protocol of wide potential utility.
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