Copper-catalyzed regioselective <i>trans</i>-silaboration of internal arylalkynes with stereochemical switch to <i>cis</i>-addition mode

Ohmura, Toshimichi; Takaoka, Yuta; Suginome, Michinori

doi:10.1039/d1cc01579f

“…Upon treatment with PhB(pin), 3aa was converted to the corresponding oxaborole 8 in 85% yield, which overall addresses an entry to the rare anti-silylboration. [42][43] The reaction with Me3SiCl gave the 1,2-disilylated product 9 in 72% yield after quickly hydrolyzing the incipient O-silyl group of the crude material in methanol. The transformation represents a rare example of anti-disilylation of alkynes.…”

Section: Resultsmentioning

confidence: 99%

Regioselective anti-Silyllithiation of Propargylic Alcohols

Karad

¹

,

Saito

²

,

Shimokawa

³

et al. 2022

Preprint

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Among the known hydrosilylation or carbosilylation conditions of alkynes, anti-addition of the two units across the triple bond is considered rare compared to the syn counterpart. For anti-silylative vicinal difunctionalizations, transition-metal catalysts, such as ruthenium or palladium complexes, are generally required. Accordingly, silyl alkali metals have not been employed for those anti-addition transformations. Here we demonstrate that silyllithiums can add across the triple bond of a series of propargylic alkoxides regioselectively in an anti-fashion. Upon treatment with a variety of electrophiles, the tri-substituted alkenyl lithium intermediates were transformed into highly functionalized β-silyl allylic alcohols with high regio-control, eventually providing tri- or tetrasubstituted alkenylsilanes stereoselectively. A classic trick for anti-addition with propargylic alkoxides has transformed anti-silylative functionalizations into a robust and reliable strategy.

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“…A simple combination of CuI and NaO t Bu under mild conditions led to the products in moderate to excellent yields. Simultaneously, Ohmura/Suginome developed the anti ‐silaboration by using a CuCl/CyJohnPhos catalytic system and showed a stereoselectivity switch depending on the solvent [119b] …”

Section: Elementoboration Of Alkynesmentioning

confidence: 99%

Synthesis of Tri‐ and Tetrasubstituted Alkenyl Boronates from Alkynes

Altarejos

¹

,

Valero

²

,

Manzano

³

et al. 2022

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The synthesis of organoboron compounds have attracted the attention of the synthetic community. In particular, molecules with C(sp2)‐B bonds enable the transformation to new C−C or C‐heteroatom bonds by well‐established methodologies. Alkenyl boronates have the possibility for further conversion of the boron moiety or functionalization of the double bond. This review gives an overview on the recent methodologies for the selective preparation of the challenging highly substituted alkenyl boronates from alkynes.

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“…Upon treatment with PhB(pin), 3aa was converted to the corresponding oxaborole 8 in 85% yield, which overall addresses an entry to the rare anti-silylboration. 41,42 The reaction with Me3SiCl gave the 1,2-disilylated product 9 in 72% yield after quickly hydrolyzing the incipient O-silyl group of the crude material in methanol. The transformation represents a rare example of anti-disilylation of alkynes.…”

Section: Scheme 1 Anti-additions For Silylative Transformations Acros...mentioning

confidence: 99%

Regioselective anti-Silyllithiation of Propargylic Alcohols

Karad

¹

,

Saito

²

,

Shimokawa

³

et al. 2022

Preprint

0

View full text Add to dashboard Cite

Among the known hydrosilylation or carbosilylation conditions of alkynes, anti-addition of the two units across the triple bond is considered rare compared to the syn counterpart. For anti-silylative vicinal difunctionalizations, transition-metal catalysts, such as ruthenium or palladium complexes, are generally required. Accordingly, silyl alkali metals have not been employed for those anti-addition transformations. Here we demonstrate that silyllithiums can add across the triple bond of a series of propargylic alkoxides regioselectively in an anti-fashion. Upon treatment with a variety of electrophiles, the tri-substituted alkenyl lithium intermediates were transformed into highly functionalized β-silyl allylic alcohols with high regio-control, eventually providing tri- or tetrasubstituted alkenylsilanes stereoselectively. A classic trick for anti-addition with propargylic alkoxides has transformed anti-silylative functionalizations into a robust and reliable strategy.

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Copper-catalyzed regioselective trans-silaboration of internal arylalkynes with stereochemical switch to cis-addition mode

Abstract: Copper-catalyzed silafunctionalization of alkynes using a silylboronic ester as a silicon souce has recently progressed rapidly. Generally, the reaction affords a product with cis-stereoselectivity. We herein describe trans-selective 1,2-addition of...

Cited by 14 publications

References 30 publications

Regioselective anti-Silyllithiation of Propargylic Alcohols

Regioselective anti-Silyllithiation of Propargylic Alcohols

Synthesis of Tri‐ and Tetrasubstituted Alkenyl Boronates from Alkynes

Regioselective anti-Silyllithiation of Propargylic Alcohols

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