An Enantioselective, Intermolecular α-Arylation of Ester Enolates To Form Tertiary Stereocenters

Huang, Zhiyan; Liu, Zheng; Zhou, Jianrong Steve

doi:10.1021/ja2066829

Cited by 113 publications

(67 citation statements)

References 25 publications

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“…14 We have also developed a catalytic method 15 for direct oxidation of enantiomerically enriched alkenyl–B(pin) products to carboxylic acids (Scheme 6). 16 Enantioselective synthesis of nonsteroidal anti-inflammatory agent ( S )-naproxen was carried out on 2.0 mmol scale with 1.0 mol % of 6b , affording the acid in 75% overall yield and 95:5 er (94% es).…”

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confidence: 99%

Catalytic Enantioselective Protoboration of Disubstituted Allenes. Access to Alkenylboron Compounds in High Enantiomeric Purity

2014

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Proto-boryl additions to 1,1-disubstituted allenes in the presence of 1.0–5.0 mol % of chiral NHC–Cu complexes, B2(pin)2, and t-BuOH proceed to afford alkenyl–B(pin) products in up to 98% yield, >98:2 site selectivity, and 98:2 er. The enantiomerically enriched alkenylboron products can be converted to otherwise difficult-to-access alkenyl bromides, methyl ketones or carboxylic acids. What’s more, the corresponding boronic acids may be used in highly stereoselective NHC−Cu-catalyzed allylic substitution reactions.

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confidence: 99%

Catalytic Enantioselective Protoboration of Disubstituted Allenes. Access to Alkenylboron Compounds in High Enantiomeric Purity

2014

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“…In a continuation of their recent work on palladium-catalyzed arylation of esters, 31 Zhou and coworkers described the synthesis of two new chiral phosphines that enable the first general method for asymmetrical a-arylation of lactones to produce tertiary stereogenic centers with high enantioselectivity (Scheme 17). 32 Various aromatic triflates were coupled to diverse lactones, affording the expected products in excellent yields and selectivities.…”

Section: Scheme 13mentioning

confidence: 99%

Recent Developments in Inter- and Intramolecular Enolate Arylation

Fernández‐Nieto

Clayden

2015

Reference Module in Chemistry, Molecular Sciences and Chemical Engineering

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“…Nevertheless, asymmetric arylation to generate less-substituted centres is possible (Scheme 2.143). 173 The use of silyl enol ethers as enolate precursors allowed the avoidance of strongly basic conditions. A hard but mildly basic nucleophile, acetate, was included to liberate the enolate.…”

Section: Enolate and Phenoxide Couplingmentioning

confidence: 99%

Coupling Reactions

2012

Organic Synthesis Using Transition Metals

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The coupling of an organometallic and an organic halide should be a useful way of forming a C-C single bond. The reaction is, however, not general, but restricted to special cases. Grignard reagents will react efficiently with some halides, such as allyl halides, while copper reagents can be used in this type of reaction with a wider range of substrates. Even so, that range is not great and copper reagents are thermally unstable, as well as sensitive to air and moisture.A useful method would not require special conditions, be quite general and use easily prepared starting materials. This can be done with transition-metal catalysis (Scheme 2.1). By far the most widely used metal is palladium, but other metals, especially nickel and, more recently, iron, have also been employed. 1 The main variables to consider are the "R" and "R " groups that can be employed, the main group metals "M" that can be used, the nature of the leaving group "X" and the identity and quantity of the ligand "L". The basic mechanism for palladium-catalysed coupling is a simple combination of oxidative addition, transmetallation and reductive elimination (Scheme 2.2).A coordinatively unsaturated palladium(0) complex 2.1, which is the catalytic species, is generated from an 18-electron palladium(0) complex by reversible ligand dissociation. Alternatively, it can be generated by reduction of a palladium(II) complex. Both the L 4 Pd and the L 2 PdX 2 should be regarded as "pre-catalysts". The catalyst or pre-catalyst complex may be assembled in situ from a mixture of a palladium source, such as a palladium(II) salt, Pd 2 (dba) 3 or even, in a few cases, palladium on carbon, and the ligand. This avoids the need to preform a palladium complex.If a palladium(II) pre-catalyst is employed, then there must be a reduction step prior to the start of the catalytic process. This has sometimes been done by the addition of a reducing agent, but more commonly, the palladium(II) is reduced by homocoupling of the organometallic partner, RM (Scheme 2.3). This homocoupling reaction is of occasional synthetic use itself (see Section 2.10).So how do we know which catalyst to employ? It is determined by looking for precedent and by doing experiments. Key variables are the ligand to metal ratio, and the identity of the ligand. Historically, Ph 3 P has been the most widely used, but that doesn't mean it is best (although it is cheapest). A less widely explored variable is the metal.

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An Enantioselective, Intermolecular α-Arylation of Ester Enolates To Form Tertiary Stereocenters

Cited by 113 publications

References 25 publications

Catalytic Enantioselective Protoboration of Disubstituted Allenes. Access to Alkenylboron Compounds in High Enantiomeric Purity

Catalytic Enantioselective Protoboration of Disubstituted Allenes. Access to Alkenylboron Compounds in High Enantiomeric Purity

Recent Developments in Inter- and Intramolecular Enolate Arylation

Coupling Reactions

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