Stereochemical Control in Organic Synthesis Using Silicon-Containing Compounds

Fleming, Ian; Barbero, Asunción; Walter, David

doi:10.1021/cr941074u

Cited by 884 publications

(318 citation statements)

References 977 publications

(1,814 reference statements)

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“…Thus, the absolute configuration of aldehydes 3 is S when R = aryl. 1 H NMR and HR-MS analyses of the crude reaction mixture confirmed that a chiral iminium intermediate was formed between catalyst 5a and enal 2a. Furthermore, no ECA product was formed when cinnamic esters were used as substrates [Eq.…”

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confidence: 86%

“…[1] In this context, the transition metal-catalyzed enantioselective conjugate addition (ECA) of in situ generated Si nucleophiles derived from readily available sources [e.g., Cl 2 PhSi À SiMe 3 and Me 2 PhSi À BA C H T U N G T R E N N U N G (pin) 1, (pin) = pinacolato] to a,b-unsaturated acceptors is particularly attractive as it provides direct access to synthetically useful b-silyl carbonyl compounds. [2][3][4][5][6][7] For example, they can be readily transformed to the corresponding b-hydroxy carbonyl compounds without competing reactions (e.g., retro-aldol).…”

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confidence: 99%

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Enantioselective Conjugate Silyl Additions to α,β‐Unsaturated Aldehydes Catalyzed by Combination of Transition Metal and Chiral Amine Catalysts

et al. 2011

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Abstract:We report that transition metal-catalyzed nucleophilic activation can be combined with chiral amine-catalyzed iminium activation as exemplified by the unprecedented enantioselective conjugate addition of a dimethylsilanyl group to a,b-unsaturated aldehydes. These reactions proceed with excellent 1,4-selectivity to afford the corresponding bsilyl aldehyde products 3 in high yields and up to 97:3 er using inexpensive bench stable copper salts and simple chiral amine catalysts. The reaction can also generate a quaternary stereocenter with good enantioselectivity. Density functional calculations are performed to elucidate the reaction mechanism and the origin of enantioselectivity.

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confidence: 86%

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confidence: 99%

Enantioselective Conjugate Silyl Additions to α,β‐Unsaturated Aldehydes Catalyzed by Combination of Transition Metal and Chiral Amine Catalysts

et al. 2011

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“…[9] The cross-linking of silicone polymers by hydrosilylation represents one of the largest applications of homogeneous catalysis on an industrial scale. [6] To date, hydrosilylation has been dominated by precious metal catalysts such as platinum, palladium, ruthenium and rhodium, however these catalysts can suffer from competitive alkene isomerisation, dehydrosilylation reactions, and incompatibility with amino-substituted olefins.…”

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confidence: 99%

Iron‐Catalysed Chemo‐, Regio‐, and Stereoselective Hydrosilylation of Alkenes and Alkynes using a Bench‐Stable Iron(II) Pre‐Catalyst

2014

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The chemo-, regio-, and stereoselective iron-catalysed hydrosilylation of alkenes and alkynes with excellent functional group tolerance is reported (34 examples, 41-96% yield). The catalyst and reagents are commercially available and easy to handle, with the active iron catalyst being generated in situ, thus providing a simple and practical methodology for iron-catalysed hydrosilylation. The silane products can be oxidised to the anti-Markovnikov product of olefin hydration, and the one-pot iron-catalysed hydrosilylation-oxidation of olefins to give silane(di)ols directly is also reported. The iron pre-catalyst was used at loadings as low as 0.07 mol%, and displayed catalyst turnover frequencies (TOF) approaching 60,000 mol h À1. Initial mechanistic studies indicate an iron(I) active catalyst.Keywords: catalysis; hydrosilylation; iron; olefins; synthetic methods Iron offers significant advantages as a catalyst over precious metals due to its low toxicity, low cost, natural abundance and sustainable long-term commercial availability.[1] Although iron catalysis is well established for cross-coupling [2] and redox reactions, [3] the hydrofunctionalisation of olefins has been less developed. In part, this can be attributed to the procedurally challenging reaction conditions and catalyst syntheses required, in comparison to the simplicity of ironcatalysed cross-coupling reactions. Building upon our work, [4] and previous work of others, [5] in which lowvalent iron catalysts were generated in situ, we sought to develop an operationally simple iron-catalysed hydrosilylation of olefins, in which all reagents were inexpensive, widely available and bench-stable. Furthermore, we sought to use this method for the introduction of silyl groups which could undergo further synthetic transformations (Figure 1).The hydrosilylation of alkenes and alkynes can produce alkyl-, allyl-, and vinylsilanes, [6] which are used in fine chemical synthesis for stereospecific oxidation [7] and cross-coupling reactions, [8] amongst other applications (Figure 1).[9] The cross-linking of silicone polymers by hydrosilylation represents one of the largest applications of homogeneous catalysis on an industrial scale.[6] To date, hydrosilylation has been dominated by precious metal catalysts such as platinum, palladium, ruthenium and rhodium, however these catalysts can suffer from competitive alkene isomerisation, dehydrosilylation reactions, and incompatibility with amino-substituted olefins.

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“…17 Optically active hydroxy silanes have been employed as a chiral auxiliary for oxocarbenium ion, 18 and they have been used for the synthesis of chiral alcohol by rearrangement of -acetoxy silane. 19 The present method for reduction of ketone with chiral alcohol 2 was applied to asymmetric reduction 20 of acyl silanes 21 for synthesis of optically active -hydroxy silanes.…”

Section: Asymmetric Reduction Of Acyl Silanesmentioning

confidence: 99%

Asymmetric reduction of aliphatic ketones and acyl silanes using chiral anti-pentane-2,4-diol and a catalytic amount of 2,4-dinitrobenzenesulfonic acid

et al. 2010

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Abstract-Aliphatic ketones were reduced to the corresponding secondary alcohols by using anti-1,3-diol and a catalytic amount of 2,4-dinitrobenzenesulfonic acid (DNBSA) in benzene at reflux. Addition of 1-octanethiol in that media improved the efficiency of the reduction. Asymmetric reduction of aliphatic ketones was performed by using chiral anti-pentane-2,4-diol, and highly asymmetric induction (up to >99% ee) was observed in the reduction of tert-alkyl ketones. Asymmetric reduction of acyl silanes using chiral antipentane-2,4-diol and DNBSA proceeded efficiently in the absence of octanethiol and the corresponding -silyl alcohols were obtained in high yields with high ees.

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Stereochemical Control in Organic Synthesis Using Silicon-Containing Compounds

Cited by 884 publications

References 977 publications

Enantioselective Conjugate Silyl Additions to α,β‐Unsaturated Aldehydes Catalyzed by Combination of Transition Metal and Chiral Amine Catalysts

Enantioselective Conjugate Silyl Additions to α,β‐Unsaturated Aldehydes Catalyzed by Combination of Transition Metal and Chiral Amine Catalysts

Iron‐Catalysed Chemo‐, Regio‐, and Stereoselective Hydrosilylation of Alkenes and Alkynes using a Bench‐Stable Iron(II) Pre‐Catalyst

Asymmetric reduction of aliphatic ketones and acyl silanes using chiral anti-pentane-2,4-diol and a catalytic amount of 2,4-dinitrobenzenesulfonic acid

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