Strained silacycle-catalyzed asymmetric Diels–Alder cycloadditions: the first highly enantioselective silicon Lewis acid catalyst

Kubota, Katsumi; Hamblett, Christopher L.; Wang, Xiaolun; Leighton, James L.

doi:10.1016/j.tet.2006.06.076

Cited by 40 publications

(25 citation statements)

References 30 publications

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“…Yes, Ozerov and co‐workers9 and likewise Müller and co‐workers10 had identified silylium ions to be catalytically active in C(sp 3 )F bond activation 11. Conversely, the self‐evident use of silylium ions in Lewis acid catalysis is elusive,12–16 presumably because of the irreversible formation of Lewis pairs.…”

Section: Methodsmentioning

confidence: 99%

Taming the Silylium Ion for Low‐Temperature Diels–Alder Reactions

2009

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Some like it hot: A novel silicon‐based Lewis acid having a trivalent silicon cation stabilized by an electron‐rich transition metal as the “hot” Lewis acidic site catalyzes challenging Diels–Alder reactions at low temperatures with excellent reaction rates and selectivities (see scheme). In addition to the chemical stability of the silylium ion catalyst (in CH2Cl2), the potential of these reactive compounds is also discussed.

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Section: Methodsmentioning

confidence: 99%

Taming the Silylium Ion for Low‐Temperature Diels–Alder Reactions

2009

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“…6 Additionally, Leighton and coworkers have demonstrated that chiral silicon complexes can serve as reagents for asymmetric crotylation reactions and as catalysts for Diels-Alder additions. 7 Based on these promising results, we were interested in exploring the behavior of neutral silicon compounds as potent Lewis acids. Herein, we report the synthesis and reactivity of a neutral bis(perfluorocatecholato)silane Lewis acid, which represents the first example of a neutral silicon species that catalyzes aldehyde hydrosilation.…”

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confidence: 99%

Lewis Acidity of Bis(perfluorocatecholato)silane: Aldehyde Hydrosilylation Catalyzed by a Neutral Silicon Compound

2015

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Bis(perfluorocatecholato)silane Si(catF)2 was prepared, and stoichiometric binding to Lewis bases was demonstrated with fluoride, triethylphosphine oxide, and N,N′-diisopropylbenzamide. The potent Lewis acidity of Si(catF)2 was suggested from catalytic hydrosilation and silylcyanation reactions with aldehydes. Mechanistic studies of hydrosilation using an optically active silane substrate, R-(+)-methyl(1-napthyl)phenylsilane, proceeded with predominant stereochemical retention at silicon, consistent with a carbonyl activation pathway. The enantiospecificity was dependent on solvent and salt effects, with increasing solvent polarity or addition of NBu4BArF4 leading to a diminished enantiomeric ratio. The medium effects are consistent with an ionic mechanism, wherein hydride transfer occurs prior to silicon–oxygen bond formation.

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“…We note as well that this analysis may facilitate a richer understanding of the origin of activity in our previously reported chiral silane Lewis acid catalyst for Diels-Alder reactions. 19 …”

Section: Resultsmentioning

confidence: 99%

A new and more powerfully activating diamine for practical and scalable enantioselective aldehyde crotylsilylation reactions

2013

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A new diaminophenol ligand for crotylsilylation reactions with cisand trans-crotyltrichlorosilane has been developed. The conformational constraints that result from the tethering of the phenol to one of the amino groups attenuate the stereoelectronic effects that reduce activity in the corresponding untethered diaminosilanes, and the resulting crotylsilane reagents are as active as our previously reported EZ-CrotylMix reagents, but without requiring the use of the Sc(OTf) 3 catalyst. In turn, this has allowed the development of an experimentally straightforward, sustainable, efficient, and scalable onepot procedure which may be carried out in #8 hours, and in which the diaminophenol activator ligand may be easily recovered in $90% yield by recrystallization.Scheme 1 (A) The procedure for the synthesis and isolation of the EZ-Cro-tylMixes. (B) Attempts to form and employ the EZ-CrotylMixes in situ are unsuccessful.

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Strained silacycle-catalyzed asymmetric Diels–Alder cycloadditions: the first highly enantioselective silicon Lewis acid catalyst

Cited by 40 publications

References 30 publications

Taming the Silylium Ion for Low‐Temperature Diels–Alder Reactions

Taming the Silylium Ion for Low‐Temperature Diels–Alder Reactions

Lewis Acidity of Bis(perfluorocatecholato)silane: Aldehyde Hydrosilylation Catalyzed by a Neutral Silicon Compound

A new and more powerfully activating diamine for practical and scalable enantioselective aldehyde crotylsilylation reactions

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