Conjugate Addition Of Dialkylzinc Reagents Research Articles

Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors.

We present here a stereoselective tandem reaction based on the asymmetric conjugate addition of dialkylzinc reagents to unsaturated acylimidazoles followed by trapping of the intermediate zinc enolate with carbocations. The use of a chiral NHC ligand provides chiral zinc enolates in high enantiomeric purities. These enolates are reacted with highly electrophilic onium compounds to afford densely substituted acylimidazoles. DFT calculations helped to understand the reactivity of the zinc enolates derived from acylimidazoles and allowed their comparison with metal enolates obtained by other conjugate addition reactions.

Stereodivergent Construction of 1,3‐Chiral Centers via Tandem Asymmetric Conjugate Addition and Allylic Substitution Reaction

AbstractHerein, we report a synthesis of cyclohexanones bearing multi‐continuous stereocenters by combining copper‐catalyzed asymmetric conjugate addition of dialkylzinc reagents to cyclic enones with iridium‐catalyzed asymmetric allylic substitution reaction. Good to excellent yields, diastereoselectivity and enantioselectivity can be obtained. Unlike the stereodivergent construction of adjacent stereocenters (1,2‐position) reported in the literature, the current reaction can achieve the stereodivergent construction of nonadjacent stereocenters (1,3‐position) by a proper combination of two chiral catalysts with different enantiomers.

Stereodivergent Construction of 1,3-Chiral Centers via Tandem Asymmetric Conjugate Addition and Allylic Substitution Reaction.

Herein, we report a synthesis of cyclohexanones bearing multi-continuous stereocenters by combining copper-catalyzed asymmetric conjugate addition of dialkylzinc reagents to cyclic enones with iridium-catalyzed asymmetric allylic substitution reaction. Good to excellent yields, diastereoselectivity and enantioselectivity can be obtained. Unlike the stereodivergent construction of adjacent stereocenters (1,2-position) reported in the literature, the current reaction can achieve the stereodivergent construction of nonadjacent stereocenters (1,3-position) by a proper combination of two chiral catalysts with different enantiomers.

Copper-catalyzed enantioselective 1,4-conjugate addition of dialkylzinc reagents to α,β- and α,β,γ,δ-unsaturated ketones

An enantioselective Cu(II)-catalyzed conjugate addition of dialkylzinc reagents to α,β- or α,β,γ,δ-unsaturated ketones with chiral cyclohexane-based amidophosphine ligands was developed. With 2 mol% of Cu(OAc)2·H2O/L5, the conjugate addition of diethylzinc to α,β-unsaturated ketones was achieved in good-to-excellent yields (up to 98%) and high enantioselectivities (up to 92% ee). This catalytic system was shown to be efficient for the 1,4-conjugate addition of Et2Zn to (2E,4E)-1,5-diphenylpenta-2,4-dien-1-one with 85% yield and 90% ee. Moreover, with 1 mol% of Cu(OTf)2/L11, the conjugate addition of α,β,γ,δ-unsaturated ketones was accomplished with 1,4-regioselectivity, good yields (79–86%) and excellent enantioselectivities (up to 97% ee).

Palladium-Catalyzed Carbonylative Conjugate Addition of Dialkylzinc Reagents

Palladium-Catalyzed Carbonylative Conjugate Addition of Dialkylzinc Reagents

ChemInform Abstract: Pd‐Catalyzed Carbonylative Conjugate Addition of Dialkylzinc Reagents to Unsaturated Carbonyls.

The Pd-catalyzed addition of organozinc reagents to unsaturated carbonyls in the presence of carbon monoxide provides 1,4-diketones in good yield. The reaction was studied with a number of substituted cyclic and acyclic ketones as well as α,β-unsaturated aldehydes.

Pd-catalyzed carbonylative conjugate addition of dialkylzinc reagents to unsaturated carbonyls.

The Pd-catalyzed addition of organozinc reagents to unsaturated carbonyls in the presence of carbon monoxide provides 1,4-diketones in good yield. The reaction was studied with a number of substituted cyclic and acyclic ketones as well as alpha,beta-unsaturated aldehydes.

ChemInform Abstract: Catalytic Asymmetric Conjugate Addition of Dialkylzinc Reagents to α,β‐Unsaturated Sulfones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic asymmetric conjugate addition of dialkylzinc reagents to α,β-unsaturated sulfones

An efficient method is reported for the highly enantioselective copper-catalyzed conjugate addition of dialkylzinc reagents to alpha,beta-unsaturated sulfones using a monodentate phosphoramidite ligand.

ChemInform Abstract: Copper‐Catalyzed Enantioselective Conjugate Addition of Dialkylzinc Reagents to α′‐Oxy Enones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Copper‐Catalyzed Enantioselective Conjugate Addition of Dialkylzinc Reagents to α′‐Oxy Enones

Broad tolerance: A step further in the enantioselective Cu-catalyzed conjugate addition of R2Zn reagents to enoyl systems is taken by using sterically encumbered α′-oxy enone templates (see scheme). The method constitutes an advanced entry to enantioenriched β-branched carboxylic acids and aldehydes with a broad R2Zn and functional group tolerance.

ChemInform Abstract: Amidophosphane—Copper(I)‐Catalyzed Asymmetric Conjugate Addition of Dialkylzinc Reagents to Racemic 6‐Substituted Cyclohexenones to Form 2,5‐Di‐ and 2,2,5‐Trisubstituted Cyclohexanones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric conjugate additions of dialkylzinc reagents to enones promoted by new purely atropisomeric phosphoramidite ligands

Enantiopure 1,1’-binaphthylazepine was employed in the preparation of two new phosphoramidites by reaction of the corresponding dichlorophosphoramidite with (R)- or (S)BINOL. In such compounds the chirality of both diol and amine moieties is only due to atropisomerism. Their catalytic efficiency was tested in the enantioselective copper-catalyzed conjugate addition of dialkylzinc reagents to acyclic, cyclic and macrocyclic α,β-unsaturated ketones. Interestingly, the diastereoisomeric ligands provided the same enantioselectivity in the addition to chalcone, but worked differently with cyclic and macrocyclic enones. The best result, as far as enantiomeric excess is concerned, was observed in the conjugate addition of Me2Zn to 2-cyclopentadecenone, affording the valuable fragrance (-) muscone in 84%ee.

Amidophosphane–Copper(I)‐Catalyzed Asymmetric Conjugate Addition of Dialkylzinc Reagents to Racemic 6‐Substituted Cyclohexenones to Form 2,5‐Di‐ and 2,2,5‐Trisubstituted Cyclohexanones

The asymmetric conjugate addition of dialkylzinc reagents to racemic 6-substituted cyclohexenones under the catalysis of chiral amidophosphane-copper(I) complexes gave a mixture of nearly equal amounts of the corresponding trans- and cis-disubstituted cyclohexanones with extremely high catalyst-controlled enantioselectivity. Epimerization with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) led to the conversion of these mixtures into the thermodynamically more stable trans-2,5-disubstituted cyclohexanone as the major product with up to 96% ee in up to 96% yield. The regio- and stereoselective alkylation of the disubstituted cyclohexanone products via the thermodynamically favored enolate gave 2,2,5-trisubstituted cyclohexanones with a quaternary asymmetric carbon atom in good yield.

Conjugate Addition/Ireland−Claisen Rearrangements of Allyl Fumarates: Simple Access to Terminally Differentiated Succinates

The conjugate addition of dialkylzinc reagents to allyl fumarates with subsequent Ireland-Claisen rearrangement has been accomplished yielding substituted unsymmetrical succinic acid derivatives. This one-pot reaction creates two new carbon-carbon bonds at contiguous stereogenic centers. The reaction proceeds for several alkylzinc reagents and substituted allyl fumarates. The products contain distinguishable functional handles for further manipulation.

Asymmetric Synthesis of All‐Carbon Benzylic Quaternary Stereocenters via Cu‐Catalyzed Conjugate Addition of Dialkylzinc Reagents to 5‐(1‐Arylalkylidene) Meldrum′s Acids.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Highly Enantioselective Copper‐Phosphoramidite‐Catalyzed Conjugate Addition of Dialkylzinc Reagents to Acyclic α,β‐Unsaturated Imides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Copper-Catalyzed Conjugate Addition of Dialkylzinc Reagents

Copper-Catalyzed Conjugate Addition of Dialkylzinc Reagents

Asymmetric Synthesis of All-Carbon Benzylic Quaternary Stereocenters via Cu-Catalyzed Conjugate Addition of Dialkylzinc Reagents to 5-(1-Arylalkylidene) Meldrum's Acids

The asymmetric synthesis of all-carbon benzylic quaternary stereocenters has been successfully achieved through copper-catalyzed addition of dialkylzinc reagents to 5-(1-arylalkylidene) and 5-(dihydroindenylidene) Meldrum's acids in the presence of phosphoramidite ligand. The resulting benzyl-substituted Meldrum's acids and 1,1-disubstituted indanes were obtained in good yields and up to 99% ee. The significance of substituting the position para, meta, and ortho to the electrophilic benzylic center was highlighted. A benzyl Meldrum's acid product was further transformed to a 3,3-disubstituted 1-indanone and a beta,beta-disubstituted pentanoic acid.

Highly Enantioselective Copper‐Phosphoramidite‐Catalyzed Conjugate Addition of Dialkylzinc Reagents to Acyclic α,β‐Unsaturated Imides

AbstractA new and practical way to introduce an alkyl fragment in the β‐position of aliphatic carboxylic acid derivatives with high enantioselectivities by the use of a commercially available chiral ligand is reported. N‐Acylpyrrolidinones, as simple derivatives of an α,β‐unsaturated carboxylic acid, were found to be the substrates of choice featuring good reactivity and high enantioselectivities (up to >99% ee).