Asymmetric Reduction Of Aromatic Ketones Research Articles

Green and scalable synthesis of chiral aromatic alcohols through an efficient biocatalytic system.

SummaryChiral aromatic alcohols have received much attention due to their widespread use in pharmaceutical industries. In the asymmetric synthesis processes, the excellent performance of alcohol dehydrogenase makes it a good choice for biocatalysts. In this study, a novel and robust medium‐chain alcohol dehydrogenase RhADH from Rhodococcus R6 was discovered and used to catalyse the asymmetric reduction of aromatic ketones to chiral aromatic alcohols. The reduction of 2‐hydroxyacetophenone (2‐HAP) to (R)‐(‐)‐1‐phenyl‐1,2‐ethanediol ((R)‐PED) was chosen as a template to evaluate its catalytic activity. A specific activity of 110 U mg−1 and a 99% purity of e.e. was achieved in the presence of NADH. An efficient bienzyme‐coupled catalytic system (RhADH and formate dehydrogenase, CpFDH) was established using a two‐phase strategy (dibutyl phthalate and buffer), which highly raised the tolerated substrate concentration (60 g l−1). Besides, a broad range of aromatic ketones were enantioselectively reduced to the corresponding chiral alcohols by this enzyme system with highly enantioselectivity. This system is of the potential to be applied at a commercial scale.

Amino acid-functionalized multi-walled carbon nanotubes: A metal-free chiral catalyst for the asymmetric electroreduction of aromatic ketones

We report new metal-free chiral electrodes for catalyzing the asymmetric reduction of aromatic ketones. Multi-walled carbon nanotubes (MWCNTs) were functionalized by chiral amino acids. The resulting amino acid-functionalized MWCNTs were fully characterized by surface analysis and spectroscopic tools and were used as a cathode for the electroreduction of 2,2,2-trifluoroacetophenone in MeCN/n-amyl alcohol (1:1)-TEAI (0.1 M). Electroreduction at l-arginine-MWCNTs and d-arginine-MWCNTs cathodes afforded, respectively, (R)- and (S)-α-(trifluoromethyl) benzyl alcohol in 60–61% yield with 43–44% enantiomeric excess (ee). The l-lysine-MWCNTs cathode gave a lower ee value of the R enantiomer (30%). The yields and ee values were a little bit lower for the electroreduction of acetophenone and other arylalkyl ketones. These amino acid-functionalized MWCNTs electrodes, in addition to showing good catalytic performance, are very stable and can be reused without loss of activity and selectivity.

Highly Enantioselective Production of Chiral Secondary Alcohols Using Lactobacillus paracasei BD101 as a New Whole Cell Biocatalyst and Evaluation of Their Antimicrobial Effects.

Chiral secondary alcohols are valuable intermediates for many important enantiopure pharmaceuticals and biologically active molecules. In this work, we studied asymmetric reduction of aromatic ketones to produce the corresponding chiral secondary alcohols using lactic acid bacteria (LAB) as new biocatalysts. Seven LAB strains were screened for their ability to reduce acetophenones to their corresponding alcohols. Among these strains, Lactobacillus paracasei BD101 was found to be the most successful at reducing the ketones to the corresponding alcohols. The reaction conditions were further systematically optimized for this strain and high enantioselectivity (99%) and very good yields were obtained. These secondary alcohols were further tested for their antimicrobial activities against important pathogens and significant levels of antimicrobial activities were observed although these activities were altered depending on the secondary alcohols as well as their enantiomeric properties. The current methodology demonstrates a promising and alternative green approach for the synthesis of chiral secondary alcohols of biological importance in a cheap, mild, and environmentally useful process.

Asymmetric Reduction of Aromatic Ketones Using Immobilized Iridium

Key words iridium - silica - asymmetric transfer hydrogenation - ketones

English

The biocatalysts for asymmetric reduction of aromatic ketones were successfully screened from soil samples polluted by substituted acetophenones. 12 strains could asymmetrically reduce acetophenone into phenethanol, while only strain YS62 possessed the best performance of reducing acetophenone into (S)-1-phenethanol. It was identified as Rhodotorula mucilaginosa based on phenotypic and genetics characteristics and it was used for further asymmetric reduction experiments of acetophenone as a new biocatalyst. R. mucilaginosa YS62 whole-cells could catalyze the asymmetric reduction of acetophenone (35 mM) into (S)-1-phenethanol (31.4 mM) with a conversion rate of 89.7% and enantiomeric excess (e.e.) of 99.9% under 60 g/L YS62 cell, pH 6.5 , 34°C for 30 h and 2% glucose as a co-substrate. These results have shown that R. mucilaginosa YS62 is a promising biocatalyst for the production of optically active phenylethanol derivatives.   Key words: Asymmetric reduction, acetophenone, Rhodotorula mucilaginosa.

ChemInform Abstract: Synthesis of a New Class of Ligands Derived from Isosorbide and Their Application to Asymmetric Reduction of Aromatic Ketones by Transfer Hydrogenation.

AbstractA variety of isosorbide‐derived amino alcohols as well as diamines such as (I) is prepared and tested as ligands in the Ru‐catalyzed asymmetric transfer hydrogenation of aromatic ketones.

Synthesis of a new class of ligands derived from isosorbide and their application to asymmetric reduction of aromatic ketones by transfer hydrogenation

A new class of β-amino alcohol and diamine ligands has been prepared from isosorbide as a chiral renewable source. The efficiency of these ligands has been evaluated for the metal-catalyzed enantioselective reduction of aromatic ketones by transfer hydrogenation, giving excellent conversion and good enantioselectivity.

ChemInform Abstract: Catalytic Enantioselective Borane Reduction of Aromatic Ketones with Sulfonyl (S)-Prolinol.

Abstract The asymmetric reduction of aromatic ketones was catalyzed by a class of recoverable and highly stable chiral sulfonamides derived from (S)-proline to yield optically active secondary alcohols in high yields and with enantiomeric excesses of up to 91%.

Adzuki bean: A new resource of biocatalyst for asymmetric reduction of aromatic ketones with high stereoselectivity and substrate tolerance

A new resource of biocatalyst for asymmetric reduction of aromatic ketones has been discovered for the first time from a common plant seed, adzuki bean, i.e. Phaseolus angularis (Willd.) W.F. Wight. The study investigated the best methods to prepare the biocatalyst and its ability to reduce ketones. Our results indicated that the biocatalyst from adzuki bean could reduce various aromatic ketones at relatively high concentrations ( e.g. 100 mM), exhibiting excellent stereoselectivity (>98% e.e.). In addition, it was found that NADPH acts as the reducing cofactor, which can be regenerated by the crude enzyme system itself using glucose as an auxiliary substrate.

Asymmetric reduction of aromatic ketones with a novel crude enzyme system from Adzuki beans

Asymmetric reduction of aromatic ketones with a novel crude enzyme system from Adzuki beans

Asymmetric Reduction of Aromatic Ketones in Pyridinium‐Based Ionic Liquids.

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.

Asymmetric reduction of aromatic ketones in pyridinium-based ionic liquids

The asymmetric reduction of aromatic ketones has been studied in pyridinium-based room temperature ionic liquids, namely, 1-ethyl-pyridinium tetrafluoroborate, [EtPy] +[BF 4] − and 1-ethyl-pyridinium trifluoroacetate, [EtPy] +[CF 3COO] −. Ionic liquids were employed as solvents, while ( R)-BINOL and ( R)-BINOL-Br were used as chiral promoters. The effects of solvent, reaction time, temperature, catalyst loading and substituents were investigated. The reduction could be easily carried out in both ionic liquids with lower catalyst loading. 1-Ethyl-pyridinium tetrafluoroborate was recycled and reused efficiently.

A Practical Synthesis of Optically Active Aromatic Epoxides via Asymmetric Transfer Hydrogenation of α‐Chlorinated Ketones with Chiral Rhodium‐Diamine Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A practical synthesis of optically active aromatic epoxides via asymmetric transfer hydrogenation of α-chlorinated ketones with chiral rhodium–diamine catalyst

A practical method for the synthesis of optically active aromatic epoxides has been developed via the formation of optically active α-chlorinated alcohols and intramolecular etherification. Optically active alcohols with up to 99% ee can be obtained from the asymmetric reduction of aromatic ketones with a substrate/catalyst ratio of 1000–5000 using a formic acid/triethylamine mixture containing a well-defined chiral Rh complex, Cp*RhCl[( R, R)-Tsdpen]. The asymmetric reduction of α-chlorinated aromatic ketones with a chiral Rh catalyst is characterized by a rapid and carbonyl group-selective transformation because of the coordinatively saturated nature of diamine-based Cp*Rh(III) hydride complexes. The outcome of the reduction is significantly influenced by the structures of the ketonic substrates as well as the hydrogen source such as formic acid or 2-propanol. Commercially available reagents and solvents can be used in this reaction without special purification. This epoxide synthetic process in either a one- or two-pot procedure is practical and particularly useful for the large-scale production of optically active styrene oxides from α-chlorinated ketones.

Asymmetric reduction of aromatic ketones catalyzed by using (αs, 4s)-2-dichloromethyl-4, 5-dihydro-α-(4-nitrophenyl)-4-oxazolemethanol-borane complex

Chiral oxazoborolidine borane complex was prepared from (αs, 4s)-2-dichloromethyl-4, 5-dihydro-α-(4-nitrophenyl)-4-oxazolemethanol with Borane in THF. The borane modified by chiral oxazoborolidine enantioselectively reduced aromatic ketones to second-alcohol with about 95% yield and medium optical yields. In the end of article, results are discussed and reduction mechanism is shown which proves the resulting major isomers fit very well.

ChemInform Abstract: Asymmetric Reduction of Aromatic Ketones by the Baker′s Yeast in Organic Solvent Systems.

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.

ChemInform Abstract: Chiral Amino‐Urea Derivatives of (1R,2R)‐1,2‐Diaminocyclohexane as Ligands in the Ruthenium Catalyzed Asymmetric Reduction of Aromatic Ketones by Hydride Transfer.

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 amino-urea derivatives of (1 R,2 R)-1,2-diaminocyclohexane as ligands in the ruthenium catalysed asymmetric reduction of aromatic ketones by hydride transfer

Several new chiral urea and thiourea ligands have been prepared by reaction of (1 R,2 R)-1,2-diaminocyclohexane with various organic isocyanates and isothiocyanates. These were used as ligands in the ruthenium catalysed enantioselective reduction of aromatic ketones by isopropanol. The reduction proceeded at room temperature using 2 mol% of ruthenium catalyst to give good yields of the ( R)-alcohol with enantiomeric excesses of up to 83%. By contrast, the use of bis-urea ligands gave much lower enantioselectivities. Amino-thiourea ligands led to the ( S)-alcohol with low enantiomeric excess.

Catalytic enantioselective borane reduction of aromatic ketones with sulfonyl ( S)-prolinol

The asymmetric reduction of aromatic ketones was catalyzed by a class of recoverable and highly stable chiral sulfonamides derived from ( S)-proline to yield optically active secondary alcohols in high yields and with enantiomeric excesses of up to 91%.

Enantiomerically pure 2-piperazinemethanols as novel chiral ligands of oxazaborolidine catalysts in enantioselective borane reductions

Abstract Novel enantiomerically pure 2-piperazinemethanols ( 3–5 ) were synthesized from 2-piperazinecar☐ylic acid 1 . The asymmetric reduction of aromatic ketones, ketimine and oxime ether has been performed with reagents prepared from 2-piprazinemethanol and borane to yield enantiomerically enriched alcohols and amines, respectively. The preferred absolute configuration of the product was dependent on the structure of the sulfonyl substituent in the chiral ligand.