Enantioselective Addition Of Dialkylzincs Research Articles

Enantioselective Addition of Dialkylzinc to Aldehydes on a Heterogeneous Magnetic Nanoparticle Catalyst

Enantioselective Addition of Dialkylzinc to Aldehydes on a Heterogeneous Magnetic Nanoparticle Catalyst

Linear β-amino alcohol catalyst anchored on functionalized magnetite nanoparticles for enantioselective addition of dialkylzinc to aromatic aldehydes.

A linear β-amino alcohol ligand, previously found to be a very efficient catalyst for enantioselective addition of dialkylzinc to aromatic aldehydes, has been anchored on differently functionalized superparamagnetic core–shell magnetite–silica nanoparticles (1a and 1b). Its catalytic activity in the addition of dialkylzinc to aldehydes has been evaluated, leading to promising results, especially in the case of 1b for which the recovery by simple magnetic decantation and reuse was successfully verified.

ChemInform Abstract: Enantioselective Addition of Organozinc Reagents to Carbonyl Compounds Catalyzed by a Camphor Derived Chiral γ‐Amino Thiol Ligand.

AbstractThe CDAT‐catalyzed enantioselective addition of dialkylzinc to aldehydes (I) and ketoesters (X) leads to corresponding alcohols (III) and (XII), respectively.

Enantioselective addition of dialkylzinc to aromatic aldimines mediated by camphor-derived chiral β-amino alcohols.

The enantioselective addition of diethylzinc or dimethylzinc to N-(diphenylphosphinoyl)imines mediated by 1 or 2 could be achieved in high yields (70-97 %) and enantioselectivities (85-98 % ee). The catalytic loading of 1 or 2 a could be reduced to 10 mol % for methylation or ethylation of imines in high yields and enantioselectivities (79-96 %) when the reaction was conducted in the presence of 1.8 equiv of methanol. N-Monosubstituted amino alcohols induced higher enantioselectivity than their N,N-disubstituted congener in our catalytic system.

ChemInform Abstract: Synthetic Approach Toward cis‐Disubstituted γ‐ and δ‐Lactones Through Enantioselective Dialkylzinc Addition to Aldehydes: Application to the Synthesis of Optically Active Flavors and Fragrances.

AbstractThe synthesis of the cis‐whisky lactone (VIIc) based on enantioselective catalysis is presented for the first time.

Synthetic approach toward cis-disubstituted γ- and δ-lactones through enantioselective dialkylzinc addition to aldehydes: application to the synthesis of optically active flavors and fragrances

A versatile and straightforward approach to optically active cis-4,5-disubstituted γ- and δ-lactones by catalytic enantioselective addition of dialkyzincs to cinnamic aldehydes and RCM ring closure has been reported. The synthetic importance of the enantioselective dialkylzinc alkylation of aldehydes has been thus widened. Such an approach has then been employed for the enantioselective synthesis of naturally occurring γ-lactone flavors like (S)-5-ethyl-butanolide (6a) and (4S,5S)-cis-whisky lactone (6b) and extended to the preparation of δ-lactones like (5S,6S)-5-methyl-6-ethylpentanolide (9a), precursor of the pheromone serricornin.

Synthesis of sterically constrained tricyclic pyrrolidinyl alcohol ligands for the enantioselective ethylation of aryl aldehydes: assessment of the influence of ring strain and N-alkyl chain length on asymmetric induction

A series of chiral sterically constrained tricyclic pyrrolidinyl alcohol ligands were synthesized from the appropriate amino acids, and a comparative study of the activity and selectivity of the ligands for the enantioselective ethylation of aromatic aldehydes was carried out. The results obtained were compared with those previously reported for related monocyclic analogues; it was found that the bicyclo[2.2.2]octane backbone fused to pyrrolidine and the groups attached to the carbinol centre, as well as the chain length of the β-amino alcohol, had a marked effect on the enantioselectivity. The enantioselective addition of dialkylzincs to aryl aldehydes in the presence of ligands with diethyl substituents on the carbinol carbon afforded ( R)- sec-alcohols in up to 99% enantiomeric excess (ee).

Highly Enantioselective Addition of Dialkylzinc to Trifluoroacetophenones, Catalyzed by 1,2-Diamines. Synthesis of Key Fragments of Inhibitors of the Enzyme 11β-HSD1 and Kinetic Analysis of the Process

Chiral diamines derived from (R,R)- or (S,S)-1,2-diphenylethylenediamine and (S)- or (R)-2,2′-bis(bromomethyl)-1,1′-binaphthalene perform very well as catalysts in the enantioselective addition of ZnEt2 and ZnMe2 to trifluoroacetophenones, avoiding reduction products, in contrast to the poor results with amino alcohols. Excellent yields (up to 99%) and high enantioselectivity (up to 92%) are achieved with the best ligands. A kinetic study at low temperature (−37 °C) shows that the reduction reaction rate on ligandless ZnEt2 is negligible (2 orders of magnitude slower) compared to the rate of addition reaction on [ZnR2(N−N)]. Using this new procedure, reported fragments of inhibitors of enzyme 11β-HSD1 that are active against obesity and type 2 diabetes mellitus, as well as new unreported modified fragments of these bioactive molecules, were produced efficiently and enantioselectively.

ChemInform Abstract: Chiral N,N-Dialkylnorephedrines as Catalysts of the Highly Enantioselective Addition of Dialkylzincs to Aliphatic and Aromatic Aldehydes. The Asymmetric Synthesis of Secondary Aliphatic and Aromatic Alcohols of High Optical Purity.

The chiral N,N-dialkylnorephedrine-catalyzed addition of dialkylzincs to aliphatic and aromatic aldehydes afforded secondary alcohols of high optical purity (to >95% ee). Among the N,N-di(primary alkyl) norephedrines, N,N-di-n-butylnorephedrine (DBNE, 3d) was found to be the most effective catalyst. 1-Phenyl-2-(1-pyrrolidinyl) propan-1-ol (3i) and N,N-diallylnorephedrine (3j) were also highly effective catalysts. The method described provides optically active secondary aliphatic alcohols of high optical purity which cannot be prepared by conventional methods

ChemInform Abstract: Asymmetric Synthesis Using Chiral Piperazines. Part 3. Enantioselective Addition of Dialkylzincs to Aryl Aldehydes Catalyzed by Chiral Piperazines.

ChemInform Abstract: Asymmetric Synthesis Using Chiral Piperazines. Part 3. Enantioselective Addition of Dialkylzincs to Aryl Aldehydes Catalyzed by Chiral Piperazines.

ChemInform Abstract: 1-Phenyl-2-(1-pyrrolidinyl)-1-propanol as a Chiral Catalyst for the Highly Enantioselective Addition of Dialkylzincs to Five-Membered Heterocyclic Aldehydes.

ChemInform Abstract: 1-Phenyl-2-(1-pyrrolidinyl)-1-propanol as a Chiral Catalyst for the Highly Enantioselective Addition of Dialkylzincs to Five-Membered Heterocyclic Aldehydes.

ChemInform Abstract: Camphordisulfonamides: Good Chiral Ligands for the Addition of Dialkylzinc to Aliphatic Aldehydes.

Abstract The preparation of several disulfonamides derived from camphor and their use in the titanium tetraisopropoxide-promoted enantioselective addition of dialkylzinc to aldehydes is described. The enantiomeric ratio is up to 98:2, the best results being obtained for aliphatic aldehydes.

ChemInform Abstract: 1,1′‐Binaphthylazepine‐Based Ligands for the Enantioselective Dialkylzinc Addition to Aromatic Aldehydes.

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.

Chiral Schiff Bases as Highly Active and Enantioselective Catalysts in Catalytic Addition of Dialkylzinc to Aldehydes

We have developed chiral Schiff base catalysts based on the ONO-tridentate ligand for the catalytic enantioselective addition of dialkylzinc to aldehydes. Various aldehydes were smoothly converted into corresponding optically active secondary alcohols with high enantioselectivity (up to 98 % ee) in high yield. Furthermore, we have succeeded in decreasing the catalyst loading minimum to 0.1 mol % in the chiral Schiff base-catalyzed enantioselective alkylation of aldehydes.

1,1′-Binaphthylazepine-based ligands for the enantioselective dialkylzinc addition to aromatic aldehydes

The new 1,1′-binaphthylazepine ligand 1c has been prepared and tested in the enantioselective addition of Et 2Zn to arylaldehydes, allowing us to reach ee’s up to 97% and giving extremely rapid reactions (10–20 min). Aminoalcohol 1c and the analogous compounds 1a and 1b were then tested in the enantioselective addition of Bu 2Zn and Me 2Zn to arylaldehydes. All of the ligands efficiently catalyze the Bu 2Zn addition to benzaldehyde, providing good yields in short reaction times (2–4 h) and high ee (up to 96%). In the enantioselective methylation of arylaldehydes ligands 1b and 1c gave high yields (88–97%) and good to high (80–90%) ee’s.

New chiral tetraaza ligands for the efficient enantioselective addition of dialkylzinc to aromatic aldehydes

A series of chiral tetraaza ligands were studied for the enantioselective addition of dialkylzinc to aldehydes. These bis(amino amide) ligands show high enantioselectivity in the addition of organozincs to aromatic aldehydes. Different structural elements on the ligands seem to play an important role in determining the observed enantioselectivity. Ligand 4b ( N, N′-bis( N- l-valinyl)-1,3-diaminopropane, with an aliphatic spacer with 3C atoms) catalyzed the addition of Et 2Zn to benzaldehyde, 1-naphtaldehyde, 4-methoxybenzaldehyde, and 4-chlorobenzaldehyde to give the corresponding alcohol products with excellent conversions and selectivities and with enantioselectivities of 99, 97, 98, and 82%, respectively. DFT calculations provide an understanding of the mechanism of the enantioselection process.

Synthesis of a series of novel N, N-dialkyl-TsDPEN ligands and their application to enantioselective addition of dialkylzinc to benzaldehyde

A series of mono- and dialkylated derivatives of C2-symmetric N-tosyl-1,2-diphenylethylene diamines have been prepared and used as ligands for the enantiomeric control of the addition of diethylzinc to aldehydes. Addition products of up to 79% ee were formed.

Application of well-defined chain-end-functionalized polystyrenes with dendritic chiral ephedrine moieties as reagents for highly catalytic enantioselective addition of dialkylzincs to aldehydes

A series of well-defined chain-end-functionalized polystyrenes having a definite number of chiral ephedrine moieties dendritically distributed at the periphery of their hyperbranched chain-ends were evaluated as chiral catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes. These dendritic macromolecules worked well as homogeneous chiral catalysts and exhibited high catalytic activity and enantioselectivity very similar to those observed for the corresponding monomeric chiral catalysts. The optimum amount of chiral catalyst was found to be 5 mol %. A profound number effect of the chiral ephedrine moieties was observed, and PS(Ephed) 8 having eight chiral ephedrine moieties at the periphery was found to be superior to other dendritic chiral catalysts. The enantioselectivity reached a value of 95% in the addition of diisopropylzinc to 3-phenylpropanal. The dendritic chiral catalysts could be easily recovered from the reaction solution by using a solvent precipitation method, and the recovered catalyst showed no significant loss of its catalytic activity or enantioselectivity.

3,3′‐Diphosphoryl‐1,1′‐bi‐2‐naphthol—Zn(II) Complexes as Conjugate Acid—Base Catalysts for Enantioselective Dialkylzinc Addition to Aldehydes.

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.

Enantioselective Dialkylzinc Addition to Aldehydes

Enantioselective dialkylzinc additions to aldehydes to generate chiral secondary alcohols are synthetically and pharmaceutically important intermediates. The authors describe the first example of conjugate acid-base catalysis which is argued to enhance catalytic activity.