C–E Bond Formation through Element–Element Addition to Carbon–Carbon Multiple Bonds

Suginome, Michinori; Matsuda, Takanori; Ohmura, Toshimichi; Seki, Akiko; Murakami, Masahiro

doi:10.1016/b0-08-045047-4/00138-2

“…Consequently, development of efficient syntheses of alkenyl boranes has received considerable attention . Hydroboration of alkynes, especially with the assistance of transition metal catalysts, is one of the most efficient and atom-economic approaches to alkenyl boranes. ,, However, an important issue in the hydroboration of alkyne is the control of selectivity (Scheme ). It is well-known that transition metal-catalyzed hydroboration of terminal alkynes proceeds regio- and stereoselectively.…”

Section: Introductionmentioning

confidence: 99%

“…The reaction generally is anti -Markovnikov and involves cis -addition. , The generally accepted mechanism for the cis -hydroboration reaction involves oxidative addition of a B–H bond to the metal center, followed by alkyne insertion, generating a metal σ-vinyl intermediate and subsequent reductive elimination (Scheme (a)) . Hydroboration of internal alkynes also involves cis -addition and forms Z -alkenyl-boronates. ,, However, the general trans -selectivity of hydroboration has remained a very challenging problem and is one of the obscure details of organoboron chemistry. Metal-free hydroboration has also been reported in recent years.…”

Section: Introductionmentioning

confidence: 99%

A Combined DFT/IM-MS Study on the Reaction Mechanism of Cationic Ru(II)-Catalyzed Hydroboration of Alkynes

Song

¹

,

Wang

²

,

Zhang

³

et al. 2017

View full text Add to dashboard Cite

Recently, the Furstner group reported the first general trans-hydroboration of internal alkynes by using a cationic ruthenium(II) complex, [Cp*Ru(MeCN) 3 ]PF 6 , as the catalyst. Density functional theory (DFT) calculations have been carried out to elucidate the reaction mechanism and the origin of stereoselectivity. The reaction mechanism was suggested to initiate with the rate-determining oxidative hydrogen migration to stereoselectively form a metallacyclopropene intermediate (that determines the trans selectivity), followed by a reductive boryl migration to form the unusual trans-addition alkenyl-borane product. A combined ion-mobility mass spectrometry (IM-MS) and DFT study has also been employed to investigate the unsuccessful reaction with terminal alkynes. Key oxidative-coupling intermediates have been identified. Our results suggest that [2 + 2 + 2] cycloaddition of terminal alkynes to form a very stable arene compound could be the reason for the unsuccessful hydroboration of the terminal alkynes. Moreover, unreactive catecholborane reagent attributes the strong coordination of its arene part with the catalyst. Our proposed nonclassical mechanism also accounted for the other related Ru(II)-catalyzed reactions (such as hydrogenation and hydrogermylation). Our combined computational and experimental study provides in-depth mechanistic understanding and insights on the unusual trans-addition catalyzed by the cationic ruthenium(II) complexes and could help design the other trans-addition reactions.

show abstract

“…[7][8][9][10][11] Particularly for the synthesis of tri-substituted alkenylsilanes, major challenges still remain in regio-and stereoselective hydrosilylation across internal alkynes. [12][13][14] These reactions proceed generally as syn-addition to the triple bond under a metal-mediated or -catalyzed conditions. Thus, development of more challenging internal anti-hydrosilylation has been actively pursued.…”

Section: Introductionmentioning

confidence: 99%

Regioselective anti-Silyllithiation of Propargylic Alcohols

Karad

¹

,

Saito

²

,

Shimokawa

³

et al. 2022

Preprint

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.

show abstract

“…[7][8][9][10][11] Particularly for the synthesis of tri-substituted alkenylsilanes, major challenges still remain in regio-and stereoselective hydrosilylation across internal alkynes. [12][13][14] These reactions proceed generally as syn-addition to the triple bond under a metal-mediated or -catalyzed conditions. Thus, development of more challenging anti-hydrosilylation has been actively pursued.…”

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.

show abstract

C–E Bond Formation through Element–Element Addition to Carbon–Carbon Multiple Bonds

Cited by 35 publications

References 278 publications

A Combined DFT/IM-MS Study on the Reaction Mechanism of Cationic Ru(II)-Catalyzed Hydroboration of Alkynes

A Combined DFT/IM-MS Study on the Reaction Mechanism of Cationic Ru(II)-Catalyzed Hydroboration of Alkynes

Regioselective anti-Silyllithiation of Propargylic Alcohols

Regioselective anti-Silyllithiation of Propargylic Alcohols

Contact Info

Product

Resources

About