Enantioselective Addition Of Dialkylzinc Reagents Research Articles

PFAM catalyzed enantioselective diethylzinc addition to imines

Chiral amines are important starting materials for the synthesis of biologically important compounds. Enantioselective addition of dialkylzinc reagents to imines is a reliable method for the synthesis of these compounds. Different chiral catalysts were developed and used for this method. Phosphorous based PFAM catalysts were tried for the first time in the enantioselective synthesis of amines by reacting diethylzinc with N-sulfonyl imines and N-diphenylphosphinoyl imines. Chiral amines were isolated with moderate to acceptable yields and enantioselectivities.

Dual stereocontrolled alkylation of aldehydes with polystyrene-supported nickel complexes derived from α-amino amides

Nickel(ii) complexes derived from α-amino amide ligands anchored to gel-type and monolithic polymers act as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes.

ChemInform Abstract: Polymer‐Supported L‐Prolinol‐Based Catalysts for the Enantioselective Addition of Dialkylzinc Reagents to N‐(Diphenylphosphinyl)imines.

AbstractThe polymeric ligand can be recovered and reused up to six times without significant loss of activity.

ChemInform Abstract: C2‐Symmetrical Nickel Complexes Derived from α‐Amino Amides as Efficient Catalysts for the Enantioselective Addition of Dialkylzinc Reagents to Aldehydes.

AbstractAliphatic aldehydes reacting with lower yields and enantioselectivities than the aromatic ones.

Polymer-supported l-prolinol-based catalysts for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinyl)imines

l-Prolinol-based ligands anchored to Merrifield or Wang-type resins have been shown to form efficient catalysts for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinyl)imines. The enantioselectivity achieved with the polymeric catalyst (ee up to 88%) is slightly lower than the one obtained with the homogeneous ligand N-benzyl-l-prolinol, but the polymer-supported ligand presents the advantage of its recyclability: it can be recovered and used in up to six consecutive catalytic cycles with only a slight decrease in the enantiomeric excess. The phosphinamides obtained as addition products can be transformed into the corresponding enantiomerically enriched α-branched primary amines under mild acidic conditions.

C2 symmetrical nickel complexes derived from α-amino amides as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes

A series of C2 symmetrical 1:2 Ni:L complexes derived from α-amino amides were studied for the enantioselective addition of dialkylzinc reagents to aldehydes. Different structural elements on the ligands seem to play an important role in determining the observed enantioselectivity. Through optimization of structure and reaction conditions, the best ligand provided secondary alcohols in excellent yields (up to 98%) and enantioselectivity of up to 99% ee for (R)-enantiomer. A transition state model has been proposed to explain the observed enantioselectivities based on computational calculations at the DFT level. Very interestingly, calculations suggest a coordination model of the aldehyde to the metal complex through association of a lone pair of the carbonyl oxygen to the hydrogen atom of an amino group.

ChemInform Abstract: Highly Enantioselective Alkylation of Carbon-Nitrogen Double Bonds. Catalytic and Stoichiometric Asymmetric Synthesis of Optically Active Amines by the Enantioselective Addition of Dialkylzinc Reagents to N- Diphenylphosphinoylimines.

ChemInform 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.

ChemInform Abstract: Catalytic Enantioselective Addition of Dialkylzinc Reagents to N‐Acylpyridinium Salts.

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 Enantioselective Addition of Dialkylzinc Reagents to N‐Acylpyridinium Salts

A pinch of salt: The first catalytic addition of dialkylzinc reagents to N-acylpyridinium salts with good yields and excellent enantioselectivities uses a copper–(S)-L complex as the catalyst. The versatility of the method is illustrated in the formal synthesis of the alkaloid (R)-coniine. Bn=benzyl, Tf=trifluoromethanesulfonyl.

ChemInform Abstract: Microwave‐Accelerated Enantioselective Addition of Dialkylzinc Reagents to N‐(Diphenylphosphinoyl)imines Catalyzed by β‐Aminoalcohols with the Proline Skeleton.

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.

Synthesis of camphorsulfonamide-based quinoline ligands and their N-oxides: first use in the enantioselective addition of organozinc reagents to aldehydes

The preparation of several camphorsulfonamide-based quinoline derivatives and their N-oxides was accomplished via an indirect Friedländer synthesis using aminobenzylic alcohols and RuCl 2(DMSO) 4 as a catalyst. These ligands were tested in the enantioselective addition of dialkylzinc reagents to aldehydes, with enantiomeric excesses up to 96%. A similar protocol using triphenylborane and diethylzinc gave the corresponding phenylation process.

Microwave-accelerated enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines catalysed by β-aminoalcohols with the prolinol skeleton

The addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines in the presence of a catalytic amount of a β-aminoalcohol with the prolinol framework under microwave irradiation gives the expected addition products in good yields and with an ee of up to 92%. The reaction times (20–30 min) are much shorter than the ones observed in the same reactions performed at room temperature without microwave irradiation. In most cases, in the microwave-promoted reactions yields improve and enantiomeric excesses are very close to the ones achieved in the reactions stirred at room temperature. High enantioselectivities are obtained in the addition of dialkylzincs to both aromatic and aliphatic imines.

ChemInform Abstract: Enantioselective Addition of Dialkylzinc Reagents to N‐(Diphenylphosphinoyl)imines Catalyzed by β‐Amino Alcohols with the Prolinol Skeleton.

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.

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.

Chiral Ligands with an Isoborneol‐10‐sulfonamide Structure: A Ten‐Year Odyssey

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 addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines catalyzed by β-aminoalcohols with the prolinol skeleton

Several β-aminoalcohols with the prolinol framework are shown to be very efficient catalysts for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines. The use of 0.5equiv of the catalyst leads to the expected addition products in good yields and with ee up to 94% in a reaction time of only 4h at room temperature. This ee is the highest value reported so far using 0.5equiv of an aminoalcohol as a promoter. High enantioselectivities are obtained in the addition of dialkylzincs to both aromatic and aliphatic imines. The amount of the catalyst can be reduced to 0.25equiv with a slight decrease in the ee. A very interesting effect of the addition rate and temperature on the enantioselectivity was also observed.

Chiral Ligands with an Isoborneol-10-sulfonamide Structure: A Ten-Year Odyssey

The isoborneol-10-sulfonamide unit represents a new type of chiral structure that has been successfully prepared and used in different reactions of organometallic addition to aldehydes and ketones. The obtained results were excellent in some cases, and this type of ligand is unique as it is able to promote the enantioselective addition of dialkylzinc reagents to simple ketones. The scope of these catalyzed reactions, together with some synthetic applications, is outlined. References to important related work from others are also included. 1 Introduction 2 First-Generation Ligands 2.1 Enantioselective Addition of Organozinc Reagents to -Aldehydes 2.2 Enantioselective Addition to Ketones 3 Second-Generation Ligands 3.1 Enantioselective Addition of Organozinc Reagents to -Aldehydes 3.2 Enantioselective Addition to Ketones 4 Third-Generation Ligands 5 Outlook

N‐Benzyl‐L‐prolinol: An Efficient Catalyst for the Enantioselective Addition of Dialkylzinc Reagents to N‐(Diphenylphosphinoyl)imines.

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.

Application of the Chiral Bis(phosphine) Monoxide Ligand to Catalytic Enantioselective Addition of Dialkylzinc Reagents to β‐Nitroalkenes.

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.

N-Benzyl- l-prolinol: an efficient catalyst for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines

Commercially available N-benzyl- l-prolinol has shown to be a very efficient catalyst for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines. The use of 0.5 equiv of this β-aminoalcohol as a catalyst leads to the expected addition products in good yields and with ees up to 92% in a reaction time of only 4 h at room temperature. This ee is almost equal to the highest value reported so far using 0.5 equiv of an aminoalcohol as promoter, although the reaction time is much shorter in our case. The amount of the catalyst can be reduced to 0.25 equiv with a slight decrease in the ee. An interesting effect of the addition rate and temperature on the enantioselectivity has been observed.