Convenient Asymmetric Borane Reduction of Ketones Catalyzed by Simple Amino Alco

An asymmetric borane reduction of prochiral ketones catalyzed by simple amino alcohols and corresponding amino acids was examined to give alcohols with e.e. value up to 92%.     

Synthesis of N-Squaramidoacids and Their Application in Asymmetric Borane Reduction of Prochiral Ketones

A series of novel N-squaramidoacid ligands were prepared conveniently. Without converting to corresponding amino alcohols, these ligands could be used in asymmetric borane reduction of prochiral aromatic ketones to give secondary alcohols in good to excellent enantiomeric excesses. The results showed that N-squaramidoacids are more efficient ligands than N-sulfonyl amino acids. N-Squaryl proline was proved to be an excellent ligand in this catalytic asymmetric process.     

Convenient Asymmetric Borane Reduction of Ketones Catalyzed by Simple Amino Alcohols and Corresponding Amino Acids

The catalytic enantioselective borane reduction of ketones is a well-studied theme1. Since the pioneering work of Corey2, a variety of good catalysts have been synthesized through further modification on simple amino alcohols and their corresponding amino acids,3,4 . But when simple amino alcohols were directly used in the reduction their catalytic efficiency was very low. For the first time Buono5 has reported through carefully chosen reaction condition the catalytic efficiency of a simple…     

Synthesis of Novel Derivatives of （R）-Cysteine and Their Application in Asymmetric Reduction of Prochiral Ketones

ovel chiral β-amino alcohols containing sulfide or sulfonyl groups were synthesized from （R）-cysteine. Their chiral induction in the asymmetric borane reduction of prochiral ketones was investigated. Optically active secondary alcohols with moderate or high e. e. values were obtained, and the causes of different enantioselectivities between these two sulfur-containing chiral β-amino alcohols were researched.     

Enantioselective Hydrogenation of α,β-Unsaturated Cyclic Ketones by Double Asymmetric Induction Preparation of (R)-Muscone

(R)-Muscone[(R)-6]isanodoriferouscomPoundisolatedfromthemalemuskdeer.BecauseofthenatUralsupplyisseverelylbotofanumberofSyntheticmethodshaveaPPearedintheliteratUre['].However,eachofthepublishedenahoselechveopthehcprocessessuffersfromoneormoreofthefollowingflollgandcomplicatedprocess,lowcheforcalandophcalvields,andscarcityofstartingmaterials[2].Inl98o,TrostetaldeveloPedashortprocesstoopthesize(dl)-musconeingoodcheforca1yteld,andthestartinmaterialiseasil3'a.ailablef3];Ouradriistoobtain(R)-mu…     

Syntheses of β－Hydroxy Ketones by Organosamarium

An organosamarium reagent was prepared via the reaction of a-bromoacetophenone with samarium. This organosamarium reagent reacted with aldehydes to give β-hydroxy ketones. A possible reaction process was suggested.     

Asymmetric Reduction of Prochiral Ketones with N‐Sulfonylated Amino Alcohols as Catalysts

Novel N‐sulfonylated amino alcohols were synthesized from L‐amino acids and (+)‐camphor, and their application to asymmetric reduction of prochiral ketones with NaBH₄–BF₃ · Et₂O is described.     

Chiral Ferrocenyl Amino Alcohols：Preparation and Application as Catalysts in the Enantioselective Reduction of Ketones Using NaBH4／I2

Five novel chiral ferrocenyl amino alcohols were prepared from natural amino acids and used as catalysts in the asymmetric reduction of prochiral ketones with NaBH4/I2 combination.The incorporation of the ferrocenyl moiety into the molecule of the chiral amino alcohols greatly improved their enantioselectivity in the catalysis.The optically active secondary alcohols were obt5ained in moderate to good enantiomeric excesses and high chemical yields.     

Enantioselective Reduction of Prochiral Ketones Catalyed by Oxazaborolidine Derived from L-Cystine

Theenantioselectivereductionofpwhralketonesisanimportantorgbocreaction.oneofthesuCCeSSulmethodsisbasedontheuseOfchindl,3,2-o.azaboroidinelpreparedfmpaminOalcoholsusuallyderivedfromQ-aminacids.bonglastdecade,manyaminoaddshavebeenusedinprepchngoxazaborolidinecataIySt,butL-cyStinehasrelativelybeenneglected.WehaveinvestigatedLcySteinederivativesinthempofenantioselectivereductionOfprOChiralke-toneswithborane2'3.Inthispaper,werePOrttwonewchiraloxazaborolidineformedinsituwith&aminoalcohols(pre…     

Asymmetric Syntheses XXVI: Catalytic Enantioselective Syntheses of β-Hydroxy Esters via Double Chiral Induction in Asymmetric Reformatsky Reactions

Catalytic asymmetric Reformatsky reactions of benzaldehyde with optically active menthyl bromoacetates in the presence of Zn-Cu couple were performed using 0.25 equiv. of (1R,2S) or (1S,2R)-dimethyl-2-amino-1,2-diphenyl ethanol as chiral ligand to obtain β - hydroxy esters with enantioselectivities up to 60.2%. The obvious double chiral induction effect was observed while chiral ligands matched with optically active substrates.     

Enantioselective Alkynylation of Ketones Promoted by β-Sulfonamide Alcohol-Titanium Complexes

A readily available β-sulfonamide alcohol-titanium complex was found to be effective on promoting the asymmetric addition reaction of an alkynylzinc reagent to unactivated simple ketones under very mild conditions. And the corresponding chiral tertiary propargylic alcohols were obtained with enantiomeric excesses of up to 86%, which provided a simple, practical and inexpensive method to generate chiral tertiary propargylic alcohols.     

Ambient Ionic Liquids Used in the Reduction of Aldehydes and Ketones

The sodium borohydride reduction of aldehydes and ketones to corresponding alcohols has been accomplished via the use of ionic liquids. The alcohols are easily obtained with excellent yields and the ionic liquid BMImBF4 could be reused.     

Reduction of 4-nitrophenol catalyzed by nitroreductase

The reduction of 4-nitrophenol catalyzed by nitroreductase in the presence of NADH was investigated in this paper.4-Amino- phenol and 4-bydroxylamino-phenol were found in the reductive products.The relationship between reaction time and the reductive ratio were studied.The similar reducing ratios of 4-nitrophenol were obtained under aerobic and anaerobic conditions.The results indicated that an oxygen-insensitive reaction was proceeded in the reduction of 4-nitrophenol and nitroreductase was an oxygen- insensitive enzyme.The reductive products of 4-nitrophenol were determined by HPLC and MS.     

Synthesis of enantiopure β-azidoalcohols from their ketoazides by reduction with NaBH4 in the presence of alumina and in situ lipase resolution

An enantioselective synthesis of chiral β-azidoalcohols via the reduction of the corresponding ketoazides with NaBH₄ in the presence of moist aluminium oxide followed by an in situ lipase-mediated resolution is described. The efficiency of various lipases and the effect of solvents have also been studied for this method. The excellent results obtained under mild reaction conditions, indicates its applicability and importance over classical methods previously reported.     

Asymmetric sulfoxidation of a β-carbonyl sulfide series by chloroperoxidase

The chloroperoxidase (CPO)-catalyzed oxidation of a series of β-carbonyl sulfides to sulfoxides has been studied at room temperature in aqueous citrate buffer. For dialkyl β-carbonyl sulfides, the products with methyl and ethyl substituents are obtained in ca. 100% yield. However when the alkyl group is n-propyl or i-propyl the yield drops dramatically (25%). An aryl sulfide derivative afforded product in very low yield (4%), but when the phenyl group bears a carbonyl, and the sulfur substituents are methyl or ethyl, the oxidation occurs with high yields (91–95%). Steric control of the sulfoxidation reaction is also confirmed with cyclohexanone derivatives, where a low product yield is observed even at high enzyme concentrations. Noteworthy are the yields obtained with cyclopentanone sulfide (65%) and an unexpected quantitative yield obtained with the γ-butyrolactone sulfide.     

Synthesis of New Chiral Phosphine Ligands and Their Application in Asymmetric Hydrogenation of Ketones

The design of new chiral ligands is the key in the development of transition metal catalyzed asymmetric synthesis. Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. Among the chiral diphosphine ligands that have been reported, the atropisomeric C2-symmetric phosphines with a biaryl scaffold initiated by Noyori and co-workers with BINAP were found to have the widest application in the transition metal catalyze…     

Guest-Binding and Catalytic Properties of Immobilized β-Cyclodextrins

Abstract

Cyclodextrins¹(CyDs), cyclic oligomers of 6–8 glucose units, form inclusion complexes with guest compounds and have been used as catalyst for the selective syntheses.² Previously, immobilization of CyD with epichlorohydrin as crosslinking agent have been described.^3-4 Here, we report the first successful immobilization of β-CyD using various crosslinking agents. The guest binding abilities and the catalytic abilities of these immobilized β-CyDs are shown.     

Emulsifying Ability of β-Cyclodextrins for Common Oils

Emulsification of various common oils was investigated using natural β-cyclodextrin (β-CD) and its derivatives as emulsifiers. An oil/water (O/W) emulsion was formed using β-CD, whereas a water/oil (W/O) emulsion was formed using tripropanoyl-β-CD and tributanoyl-β-CD derivatives. Triacetyl-β-CD gave rise to both O/W and W/O emulsions. The type of emulsion was governed by the contact angle (θ_ow), which the precipitate of CD origin make with the oil-water interface.     

Reduction of Aromatic α-Halo Ketones with Metallic Bismuth

Aromatic α-bromo ketones and α-iodio ketones can be reduced by bismuth prepared from NaBH₄ and BiCl₃ in water to their parent ketones in high yields, but aromatic α-chloro ketones should be added to sodium iodide first.     

Characteristic Studies of Arylated β-Cyclodextrins in Host-Guest Complexation with Small Molecules

Tornsshapedcyclodextrins(CDs,includingQ-,6-,y-CDetc.),whicharehydrophilicoutsideandhydrophobicinside,havegainedprominenceinrecentyearsforprovidingidealstoconstrUctefficientwtificialenZymes,molecularrecognitionsensorsandotherfunctionalmodelsl-3.ForbuildingmoreefficientartificialenZymesandmolecularrecognitionsensors'-',wehavepreparedaseriesof6-CDderivativesbearingchromophores'-',includingmono-2-O-benzoyI-9-CD(V),mono-3-O-benzoyl-0-CD(VI)andmono-6-O-benzoyl-0-CD(Vll)(Fig.l)andfoundthat3'…