Asymmetric Reduction Of Prochiral Ketones Research Articles

Enantioselective reduction of prochiral ketones by catecholborane catalysed by chiral group 13 complexes

LiGaH4, in combination with the S,O-chelate 2-hydroxy-2'-mercapto-1,1'-binaphthyl (MTBH2), forms an active catalyst for the asymmetric reduction of prochiral ketones, with catecholborane as the hydride source. Enantioface differentiation is on the basis of the steric requirements of the ketone substituents. Aryl/ n-alkyl ketones are reduced in 90-93% ee and RC(O)Me (e.g. R = iPr, cycloC6H11, tBu) in 60-72% ee. Other borane sources and alternative catalyst structures based on indium do not form enantioselective catalysts.

Asymmetric reduction of prochiral ketones using in situ generated oxazaborolidines derived from amino alcohols of (1 R)-camphor as catalysts

Chiral oxazaborolidines generated in situ from 1,2-amino alcohols and amino alcohol derivatives derived from (1 R)-(+)-camphor and borane or trimethyl borate were used as catalysts for the enantioselective reduction of prochiral ketones.

ChemInform Abstract: Optically Active Alcohols: Resolution and Synthesis from Asymmetric Reduction of Prochiral Ketones

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.

The mechanism of asymmetric reduction catalyzed by a C2 symmetric bis-amino alcohol catalyst

By means of1H,13C,11B NMR, polar transfer DEPT135, DEPT90 and 2D NMR experiments, IR, etc, the structure of the diaminodihydroxyl ligand and its derivatives used in the asym-metric reduction of prochiral ketones were detected. The catalysts derived from the ligand and borane formedin situ were also studied and the structure transformations in solution were monitored. The structure of the catalyst was proved to be a new type of dual-centered catalyst — bisoxazaborolidine.

Optically active alcohols: Resolution and synthesis from asymmetric reduction of prochiral ketones

The recent methods of resolution, enantiomeric excess determination and synthesis of optically active alcohols from asymmetric reduction of prochiral ketones are reviewed in the article with references. Important functions and applications of optically active alcohols in biological and chemical research area are described in an introduction part. The following part deals with resolution and enaniiomeric excess determination of racemic alcohols. The next part discusses asymmetric reduction of prochiral ketone and related compounds, which including: (a) Reduction by chirally modified aluminum and boron hydrides: (b) Catalytic reduction with chiral transition metal, complexes: (c) Enantioselective reduction by hydride transfer from carbon: (d) Biocatalytic reduction: (e) Asymmetric synthesis of chiral nonracemic alcohols with help of physical methods. A conclusion about optically active, alcohols from asymmetric reduction of ketones followes in the final part of article.

Enantioselective Reduction of Prochiral Ketones Using a Reagent Prepared from Lithium Aluminium Hydride, (+)Threo-1,16-Dibenzyloxy, 7(R),8(R)-Dihydroxy Hexadecane and Alcohol

Asymmetric reduction of prochiral ketones to optically active chiral secondary alcohols was achieved using a reagent prepared by modifying lithium aluminium hydride with a chiral auxiliary, (+)threo-1,16-dibenzyloxy,7,8-dihydroxy hexadecane and various additive alcohols. (+)threo-1,16-dibenzyloxy,7(R),8(R)-dihydroxy hexadecane was prepared from (+)threo-9(R),10(R),16-trihydroxy hexadecanoic acid. Alcohols such as CH3(CH2)n-OH of different chain length (n = 0–11) and (R)-hydnocarpic alcohol were used. Complex prepared from (+)threo-1,16-dibenzyloxy,7(R),8(R)-dihydroxy hexadecane, LAH and (R)-hydnocarpic alcohol reduced acetophenone in moderate enantioselectivity (maximum of 70% ee). Various arylalkylketones were reduced with the same complex.

ChemInform Abstract: Asymmetric Reduction of Prochiral Ketones with Sodium Borohydride in the Presence of Amino Deoxy Sugars.

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.

Chiral phosphinamides: new catalysts for the asymmetric reduction of ketones by borane

We have identified a new class of catalysts for the asymmetric reduction of prochiral ketones by borane. Key to the architecture of effective catalysts is an N–PO structural unit which may be part of a phosphinamide, phosphonamide or a related structure. Such catalysts are simple to prepare, are often crystalline solids and may be recovered from reduction reactions and reused. The catalysts act essentially as Lewis bases, serving to increase the reactivity of borane by electron donation. The incorporation of a hydroxy group into the catalyst provides an adjacent Lewis acid site upon reaction with borane and thus affords a superior catalyst capable of asymmetric inductions of up to 92% ee.

Cis-1-Amino-1,2,3,4-tetrahydro-2-naphthalenol: resolution and application to the catalytic enantioselective reduction of ketones

cis-1-amino-1,2,3,4-tetrahydro-2-naphthalenol was synthesized and resolved via its diastereomeric salts. Asymmetric reduction of prochiral ketones was examined using this amino alcohol at various temperatures.

Catalytic Asymmetric Reduction of Prochiral Ketones in the Presence of Chiral Quinine-Co(Ⅱ) Complex

Catalytic Asymmetric Reduction of Prochiral Ketones in the Presence of Chiral Quinine-Co(Ⅱ) Complex

ChemInform Abstract: Chiral Thiourea as Ligand for the Asymmetric Reduction of Prochiral Ketones.

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.

Chiral thiourea as ligand for the asymmetric reduction of prochiral ketones

The catalytic enantioselective reduction of prochiral ketones using a chiral thiourea as ligand is reported. Several metallic precursors were tested. e.e.'s up to 94% are obtained with a ruthenium complex.

Hydroboration. 94. Rates of Hydroboration of 2-Organylapopinenes with 9-Borabicyclo[3.3.1]nonane, ProvidingB-(2-Organylapoisopinocampheyl)-9-borabicyclo[3.3.1]nonanes, Potentially Valuable for the Asymmetric Reduction of Prochiral Ketones

Five representative enantiomerically pure, hindered terpenes, derived from α-pinene, namely 2-organylapopinenes (2-R-apopinenes, R = Et, Pr, i-Bu, Ph, and i-Pr) have been treated with 9-borabicyclo[3.3.1]nonane (9-BBN) in a 1:1 molar ratio in THF at 24 °C and the rate of hydroboration followed. Increasing the bulk of the 2-R group from the 2-methyl of α-pinene (Ipc, 2-methylapopinene) to 2-ethyl- (Eap), to 2-propyl- (Prap), to 2-isobutyl- (i-Bap), to 2-phenyl- (Pap), and to 2-isopropyl- (i-Prap) significantly lowers the rate of hydroboration with 9-BBN. Thus, the rate of hydroboration of α-pinene with 9-BBN is faster than the rates for the 2-R-apopinenes studied. The sterically bulkier 2-isobutyl-, 2-phenyl-, and 2-isopropylapopinenes reveal a significantly slower rate of hydroboration with 9-BBN. At an elevated temperature, 65 °C, the reaction of 9-BBN (1.0 equiv) with a slight excess of optically pure 2-isobutyl- and 2-phenylapopinenes (1.10−1.20 equiv), under neat conditions, is facilitated to provide ...

The asymmetric induction and catalysis of chiral reverse micelle: Asymmetric reduction of prochiral ketones

Within chiral reverse micelles formed from chiral surfactants, prochiral ketones can be reduced with NaBH 4 to optically active alcohols. The enantioselec tivity of the reaction is affected by the structures of both surfactant and substrate, and also related to the composition of the microenviroument. The presence of some sugars can effectively increase the enantiomeric excess of the products.

Enantioselective Reduction of Ketones with Sodium Borohydride, Catalyzed by Optically Active (β‐Oxoaldiminato)cobalt(II) Complexes

Asymmetric reduction of prochiral ketones with sodium borohydride proceeds in the presence of catalytic amounts of optically active β-oxoaldiminatocobalt(II) complexes 1 to the corresponding optically active secondary alcohols in high chemical yields with high enantioselectivities (68–94% ee).

Asymmetric reduction of prochiral ketones using polymer-supported catalysts and reagents

After a brief review of the literature on asymmetric reduction of prochiral ketones using polymer-supported catalysts or reagents some new results in this field are presented. In particular asymmetric reduction is reported here using (1) chiral oxazaborolidines as catalyst and BH 3 as reducing agent, and (2) polymer reagents based on supported chiral amino alcohol and BH 4 −. The best enantiomeric excess obtained with these systems is 75%.

Cis-2-Amino-1-acenaphthenol: Practical resolution and application to the catalytic enantioselective reduction of ketones

Abstract The chiral amino alcohol, cis -2-amino-1-acenaphethenol, was resolved via its ( R )-2-phenylpropionic acid salt. This amino alcohol was used as the precursor of a chiral oxazaborolidine, which was an efficient chiral catalyst in the asymmetric reduction of prochiral ketones.

ChemInform Abstract: Asymmetric Reduction of Prochiral Ketones with Sodium Borohydride in the Presence of Monosaccharide Derivatives.

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.

Asymmetric catalytic reduction of carbonyl compounds using C 2 symmetric diamines as chiral ligands

The catalytic asymmetric reduction of prochiral ketones by hydride transfer using various C 2 symmetric chiral diamines as ligands and rhodium complexes is studied. Kinetic studies show an increase of the enantiomeric excess with the conversion.

Large‐scale Production of Chiral Alcohols with High Enantiomeric Excess through Yeast‐mediated Asymmetric Reduction of Prochiral Ketones

Large‐scale Production of Chiral Alcohols with High Enantiomeric Excess through Yeast‐mediated Asymmetric Reduction of Prochiral Ketones