cas 14898-80-7, (S)-(+)-4-METHYL-2-PENTANOL

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Facile Stereoselective Reduction of Prochiral Ketones by using an F420-dependent Alcohol Dehydrogenase
Effective procedures for the synthesis of optically pure alcohols are highly valuable. A commonly employed method involves the biocatalytic reduction of prochiral ketones. This is typically achieved by using nicotinamide cofactor-dependent reductases. In this work, we demonstrate that a rather unexplored class of enzymes can also be used for this. We used an F420-dependent alcohol dehydrogenase (ADF) from Methanoculleus thermophilicus that was found to reduce various ketones to enantiopure alcohols. The respective (S) alcohols were obtained in excellent enantiopurity (>99 % ee). Furthermore, we discovered that the deazaflavoenzyme can be used as a self-sufficient system by merely using a sacrificial cosubstrate (isopropanol) and a catalytic amount of cofactor F420 or the unnatural cofactor FOP to achieve full conversion. This study reveals that deazaflavoenzymes complement the biocatalytic toolbox for enantioselective ketone reductions.
Martin, Caterina,Tjallinks, Gwen,Trajkovic, Milos,Fraaije, Marco W.
p. 156 - 159
(2020/10/26)

Pickering-Droplet-Derived MOF Microreactors for Continuous-Flow Biocatalysis with Size Selectivity
Enzymatic microarchitectures with spatially controlled reactivity, engineered molecular sieving ability, favorable interior environment, and industrial productivity show great potential in synthetic protocellular systems and practical biotechnology, but their construction remains a significant challenge. Here, we proposed a Pickering emulsion interface-directed synthesis method to fabricate such a microreactor, in which a robust and defect-free MOF layer was grown around silica emulsifier stabilized droplet surfaces. The compartmentalized interior droplets can provide a biomimetic microenvironment to host free enzymes, while the outer MOF layer secludes active species from the surroundings and endows the microreactor with size-selective permeability. Impressively, the thus-designed enzymatic microreactor exhibited excellent size selectivity and long-term stability, as demonstrated by a 1000 h continuous-flow reaction, while affording completely equal enantioselectivities to the free enzyme counterpart. Moreover, the catalytic efficiency of such enzymatic microreactors was conveniently regulated through engineering of the type or thickness of the outer MOF layer or interior environments for the enzymes, highlighting their superior customized specialties. This study provides new opportunities in designing MOF-based artificial cellular microreactors for practical applications.
Liang, Linfeng,Shi, Hu,Tian, Danping,Wang, Jun-Hao,Xue, Nan,Yang, Hengquan,Zhang, Xiaoming
supporting information
p. 16641 - 16652
(2021/10/20)

Synthesis of cis-1,2-diol-type chiral ligands and their dioxaborinane derivatives: Application for the asymmetric transfer hydrogenation of various ketones and biological evaluation
Two cis-1,2-diol-type chiral ligands (T1 and T2) and their tri-coordinated chiral dioxaborinane (T(1–2)B(1–2)) and four-coordinated chiral dioxaborinane adducts with 4-tert-butyl pyridine sustained by N → B dati
Kilic, Ahmet,Balci, Tu?ba Ersayan,Arslan, Nevin,Aydemir, Murat,Durap, Feyyaz,Okumu?, Veysi,Tekin, Recep
(2020/06/10)

Boron containing chiral Schiff bases: Synthesis and catalytic activity in asymmetric transfer hydrogenation (ATH) of ketones
Asymmetric Transfer Hydrogenation (ATH) has been an attractive way for the reduction of ketones to chiral alcohols. A great number of novel and valuable synthetic pathways have been achived by the combination usage of organometallic and coordination chemistry for the production of important class of compounds and particularly optically active molecules. For this aim, four boron containing Schiff bases were synthesized by the reaction of 4-formylphenylboronic acid with chiral amines. The boron containing structures have been found as stable compounds due to the presence of covalent B–O bonds and thus could be handled in laboratory environment. They were characterized by 1H NMR and FT-IR spectroscopy and elemental analysis and they were used as catalyst in the transfer hydrogenation of ketones to the related alcohol derivatives with high conversions (up to 99%) and low enantioselectivities (up to 22% ee).
Pa?a, Salih,Arslan, Nevin,Meri??, Nermin,Kayan, Cezmi,Bingül, Murat,Durap, Feyyaz,Aydemir, Murat
(2019/09/19)

Biaryl diphosphine ligands and their ruthenium complexes: Preparation and use for catalytic hydrogenation of ketones
Procedures for the preparation of the nucleophilic diphosphine ligands (R)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine) ((R)-Ph-Garphos, 2a) and (S)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine) ((S)-Ph-Garphos, 2b) were described. The ligands were used to prepare the ruthenium(II) Ph-Garphos complexes, chloro(p-cymene)(R)-(4,4′,6,6′-tetraamethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine)ruthenium(II) chloride ([RuCl(p-cymene)(R)-Ph-Garphos]Cl (3)) and chloro(p-cymene)(S)-(4,4′,6,6′-tetraamethoxybiphenyl-2,2′-diyl)bis(diphenylphosphine)ruthenium(II) chloride ([RuCl(p-cymene)(S)-Ph-Garphos]Cl (4)). In the presence of the chiral diamine co-ligands (1R,2R)-1,2-diphenylethane-1,2-diamine (R,R-DPEN) and (1S,2S)-1,2-diphenylethane-1,2-diamine (S,S-DPEN), complexes 3 and 4 were found to be catalyst precursors for the enantioselective reduction of aryl ketones under mild conditions (room temperature and 3–4 atm of H2). The chiral alcohols were isolated in moderate to good yields and with enantioselectivities of up to 93percent. The ruthenium complexes chloro(p-cymene)(R)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(bis(3,5-dimethylphenyl)-phosphine)ruthenium(II) chloride ([RuCl(p-cymene)(R)-Xyl-Garphos]Cl (5)) and chloro(p-cymene)(S)-(4,4′,6,6′-tetramethoxybiphenyl-2,2′-diyl)bis(bis(3,5-dimethylphenyl)-phosphine)ruthenium(II) chloride ([RuCl(p-cymene)(S)-Xyl-Garphos]Cl (6)) were also prepared and used as catalyst precursors for the hydrogenation of aryl ketones in the presence of (R,R)-DPEN and (S,S)-DPEN. Significant improvements in the enantioselectivities of the alcohols (up to 98percent ee.) were afforded. A combination of 6 and (S,S)-DPEN afforded (R)-1-(3-methoxyphenyl)ethanol in 89percent yield and with 95percent ee which was shown to be a suitable precursor for the preparation of (S)-rivastigmine.
Abdur-Rashid, Kamaluddin,Abdur-Rashid, Kareem,Dasgupta, Tara,Jia, Wenli,Lorraine, Shannen,Maragh, Paul
(2020/07/10)

Manganese Catalyzed Asymmetric Transfer Hydrogenation of Ketones Using Chiral Oxamide Ligands
The asymmetric transfer hydrogenation of ketones using isopropyl alcohol (IPA) as hydrogen donor in the presence of novel manganese catalysts is explored. The selective and active systems are easily generated in situ from [MnBr(CO)5] and inexpensive C2-symmeric bisoxalamide ligands. Under the optimized reaction conditions, the Mn-derived catalyst gave higher enantioselectivity compared with the related ruthenium catalyst.
Schneek?nig, Jacob,Junge, Kathrin,Beller, Matthias
supporting information
p. 503 - 507
(2019/02/26)

Catalysts for the asymmetric transfer hydrogenation of various ketones from [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] and [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2
The combination of [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] with [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2, in the presence of KOH/isoPrOH, has been found to generate catalysts that are capable of enantioselectively reducing alkyl, aryl ketones to the corresponding (R)-alcohols. Under optimized conditions, when the catalysts were applied to the asymmetric transfer hydrogenation, we obtained the secondary alcohol products in high conversions and enantioselectivities using only 0.5 mol% catalyst loading. In addition, [3-[(2S)-2-{[(chloro(?4-1,5-cyclooctadiene)rhodium)diphenyl phosphanyl] oxy}-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride], (6) complex is much more active than the other analogous complexes in the transfer hydrogenation. Catalyst 6 acts as excellent catalysts, giving the corresponding (R)-1-phenyl ethanol in 99% conversion in 30 min (TOF ≤ 396 h?1) and in high enantioselectivity (92% ee).
Meri?, Nermin,Arslan, Nevin,Kayan, Cezmi,Rafikova, Khadichakhan,Zazybin, Alexey,Kerimkulova, Aygul,Aydemir, Murat
p. 108 - 118
(2019/04/17)

Pickering Emulsion-Derived Liquid-Solid Hybrid Catalyst for Bridging Homogeneous and Heterogeneous Catalysis
We describe a novel method to prepare a liquid-solid hybrid catalyst via interfacial growth of a porous silica crust around Pickering emulsion droplets, which allowed us to overcome the current limitations of both homogeneous and heterogeneous catalysts. The inner micron-scaled liquid (for example, ionic liquids) pool of the resultant catalyst can host free homogeneous molecular catalysts or enzymes to create a true homogeneous catalysis environment. The porous silica crust of the hybrid catalyst has excellent stability, which makes it amenable to packing directly in fixed-bed reactors for continuous flow catalysis. As a proof of concept, the enzymatic kinetic resolution of racemic alcohols, CrIII(salen) complex-catalyzed asymmetric ring opening of epoxides and Pd-catalyzed Tsuji-Trost allylic substitution reactions were used to verify the generality and versatility of our strategy for bridging homogeneous and heterogeneous catalysis. The hybrid catalyst-based continuous flow system exhibited a 1.6a16-fold enhancement in activity relative to homogeneous counterparts even over 1500 h, and the afforded enantioselectivities were completely equal to those obtained in the homogeneous counterpart systems. Interestingly, the catalytic efficiency can be tuned through rational engineering of the porous crust and the dimensions of the liquid pool, resulting in features of an innovatively designed catalyst. This contribution provides a new method to design efficient catalysts that can bridge the conceptual and technical gaps between homogeneous and heterogeneous catalysis.
Zhang, Xiaoming,Hou, Yiting,Ettelaie, Rammile,Guan, Ruqun,Zhang, Ming,Zhang, Yabin,Yang, Hengquan
supporting information
p. 5220 - 5230
(2019/03/11)

Chiral C2-symmetric η6-p-cymene-Ru(II)-phosphinite complexes: Synthesis and catalytic activity in asymmetric reduction of aromatic, methyl alkyl and alkyl/aryl ketones
Chiral C2-symmetric bis(phosphinite) ligands and their binuclear ruthenium(II) complexes have been synthesized and used as catalysts in the ruthenium-catalyzed asymmetric transfer hydrogenation of aromatic, methyl alkyl and alkyl/aryl ketones using 2-propanol as both the hydrogen source and solvent in the presence of KOH. Under optimized conditions, all complexes showed high catalytic activity as catalysts in the reduction of various ketones to corresponding chiral secondary alcohols. Products were obtained with high conversions (99%) and moderate to good enantioselectivities (82% ee). Furthermore, C2-symmetric bis(phosphinite) ligands and their binuclear ruthenium(II) complexes were characterized by multinuclear NMR spectroscopy, FT-IR spectroscopy, LC/MS-MS and elemental analysis.
Karaka?, Duygu Elma,Aydemir, Murat,Durap, Feyyaz,Baysal, Ak?n
p. 430 - 439
(2017/12/06)

Synthesis and characterization of novel silica coated magnetic nanoparticles with tags of β-cyclodextrin: application as an eco-friendly and chiral micro-vessel catalyst in the enantioselective reduction of ketones
In this work, we report the synthesis of a novel, green and recoverable organic–inorganic magnetic nanocomposite by grafting β-cyclodextrin on the surface of a silica-coated magnetic nanoparticle, Fe3O4@SiO2/Pr-β-CD. FT-IR spectroscopy, transmission electron microscopy, CHN analysis, thermogravimetric analysis, vibrating sample magnetometer and X-ray diffraction analyses confirmed its structure. The magnetic core–shell structured modified silica microsphere has been successfully used as a chiral micro-vessel catalyst for the enantioselective reduction of ketones by NaBH4. The described catalyst was regenerated and reused without any significant changes in the yield and enantiomeric excess.
Jafari Nasab, Mina,Kiasat, Ali Reza
p. 2719 - 2728
(2018/02/06)

A new class of well-defined ruthenium catalysts for enantioselective transfer hydrogenation of various ketones
A pair of novel optically pure phosphinite ligands were synthesized by ring opening reaction of chiral amines with (R)-styrene oxide or (S)-glycidyl phenyl ether oxide using a straightforward method in high yields and their ruthenium complexes were described in detail. The ruthenium complexes proved to be highly efficient catalysts for the enantioselective hydrogenation of ketones, affording products up to 99% ee. The results showed that the corresponding chiral alcohols could be obtained with high activity and excellent enantioselectivities at the desired temperature. (2S)-1-{benzyl[(1S)-1-(naphthalen-1-yl)ethyl]amino}-3-phenoxypropan-2-yl diphenylphosphinito[dichloro(η6-benzene)ruthenium (II)] acts an excellent catalyst in the reduction of ketones, giving the corresponding alcohol up to 99% ee.
Kayan, Cezmi,Meri?, Nermin,Rafikova, Khadichakhan,Zazybin, Alexey,Gürbüz, Nevin,Karakaplan, Mehmet,Aydemir, Murat
p. 37 - 47
(2018/06/20)

CHIRAL METAL COMPLEX COMPOUNDS
The invention comprises novel chiral metal complex compounds of the formula (I) wherein M, PR2, R3 and R4 are outlined in the description, its stereoisomers, in the form as a neutral complex or a complex cation with a suitable counter ion. The chiral metal complex compounds can be used in asymmetric reactions, particularly in asymmetric reductions of ketones, imines or oximes.
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Page/Page column 18; 19; 23

(2018/11/10)

Homochiral Metal-Organic Cage for Gas Chromatographic Separations
Metal-organic cages (MOCs) as a new type of porous material with well-defined cavities were extensively pursued because of their relative ease of synthesis and their potential applications in host-guest chemistry, molecular recognition, separation, catalysis, gas storage, and drug delivery. Here, we first reported that a homochiral MOC [Zn3L2] is explored to fabricate [Zn3L2] coated capillary column for high-resolution gas chromatographic separation of a wide range of analytes, including n-alkanes, polycyclic aromatic hydrocarbons, and positional isomers, especially for racemates. Various kinds of racemates such as alcohols, diols, epoxides, ethers, halohydrocarbons, and esters were separated with good enantioselectivity and reproducibility on the [Zn3L2] coated capillary column. The fabricated [Zn3L2] coated capillary column exhibited significant chiral recognition complementary to that of a commercial β-DEX 120 column and our recently reported homochiral porous organic cage CC3-R coated column. The results show that the homochiral MOCs will be very attractive as a new type of chiral selector in separation science.
Xie, Sheng-Ming,Fu, Nan,Li, Li,Yuan, Bao-Yan,Zhang, Jun-Hui,Li, Yan-Xia,Yuan, Li-Ming
p. 9182 - 9188
(2018/07/21)

Chiral phosphinites as efficient ligands for enantioselective Ru(II), Rh(I) and Ir(III)-catalyzed transfer hydrogenation reactions
Abstract: Metal-catalyzed enantioselective transfer reduction of ketones to enantiomerically enriched chiral alcohols has recently attracted attention. Therefore, a series of methyl alkyl or alkyl/aryl ketones have been reduced by using Ru(II), Rh(I) and Ir(III) catalysts based on C2-symmetric chiral ferrocenyl phosphinite ligands. The corresponding optically active secondary alcohols were obtained in excellent conversions and moderate-to-good enantioselectivities. The best results were obtained with an iridium catalyst, giving up to 98% conversion and 80% ee.
Baysal, Ak?n,Elma Karaka?, Duygu,Meri?, Nermin,Ak, Bünyamin,Aydemir, Murat,Durap, Feyyaz
p. 365 - 372
(2017/04/18)

Manganese(I)-Catalyzed Enantioselective Hydrogenation of Ketones Using a Defined Chiral PNP Pincer Ligand
A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30–40 °C, 4 h, 30 bar H2). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry.
Garbe, Marcel,Junge, Kathrin,Walker, Svenja,Wei, Zhihong,Jiao, Haijun,Spannenberg, Anke,Bachmann, Stephan,Scalone, Michelangelo,Beller, Matthias
supporting information
p. 11237 - 11241
(2017/09/02)

In vitro biocatalytic pathway design: Orthogonal network for the quantitative and stereospecific amination of alcohols
The direct and efficient conversion of alcohols into amines is a pivotal transformation in chemistry. Here, we present an artificial, oxidation-reduction, biocatalytic network that employs five enzymes (alcohol dehydrogenase, NADP-oxidase, catalase, amine dehydrogenase and formate dehydrogenase) in two concurrent and orthogonal cycles. The NADP-dependent oxidative cycle converts a diverse range of aromatic and aliphatic alcohol substrates to the carbonyl compound intermediates, whereas the NAD-dependent reductive aminating cycle generates the related amine products with >99% enantiomeric excess (R) and up to >99% conversion. The elevated conversions stem from the favorable thermodynamic equilibrium (K′eq = 1.88 × 1042 and 1.48 × 1041 for the amination of primary and secondary alcohols, respectively). This biocatalytic network possesses elevated atom efficiency, since the reaction buffer (ammonium formate) is both the aminating agent and the source of reducing equivalents. Additionally, only dioxygen is needed, whereas water and carbonate are the by-products. For the oxidative step, we have employed three variants of the NADP-dependent alcohol dehydrogenase from Thermoanaerobacter ethanolicus and we have elucidated the origin of the stereoselective properties of these variants with the aid of in silico computational models.
Knaus, Tanja,Cariati, Luca,Masman, Marcelo F,Mutti, Francesco G.
supporting information
p. 8313 - 8325
(2017/10/19)

New functional chiral P-based ligands and application in ruthenium-catalyzed enantioselective transfer hydrogenation of ketones
Metal-catalyzed asymmetric transfer hydrogenation is a powerful and practical method for the reduction of ketones to produce the corresponding secondary alcohols, which are valuable building blocks in the pharmaceutical, perfume, and agrochemical industries. Hence, a series of novel chiral β-amino alcohols were synthesized by chiral amines with regioselective ring opening of (S)-propylene oxide or reaction with (S)-(+)-2-hydroxypropyl p-toluenesulfonate by a straightforward method. The chiral ruthenium catalytic systems generated from [Ru(arene)(μ-Cl)Cl]2 complexes and chiral phosphinite ligands based on amino alcohol derivatives were employed in asymmetric transfer hydrogenation of ketones to give the corresponding optically active alcohols; (2S)-1-{[(2S)-2-[(diphenylphosphanyl)oxy]propyl][(1R)-1-phenylethyl]amino}propan-2-yldiphenylphosphinitobis[dichol-oro(η6-benzene)ruthenium(II)] acts an excellent catalyst in the reduction of α-naphthyl methyl ketone, giving the corresponding alcohol with up to 99% ee. The substituents on the backbone of the ligands were found to have a remarkable effect on both the conversion and enantioselectivity of the catalysts. Furthermore, this transfer hydrogenation is characterized by low reversibility under these conditions.
Meri?, Nermin,Kayan, Cezmi,Gürbüz, Nevin,Karakaplan, Mehmet,Binbay, Nil Ertekin,Aydemir, Murat
p. 1739 - 1749
(2017/10/26)

Asymmetric transfer hydrogenation of ketones by N,N-containing quinazoline-based ruthenium(II) complexes
The novel set of quinazoline-based chiral ligands was synthesized starting from optically pure amino acids. Coordination with RuCl2(PPh3)dppb gave ruthenium(II) N-heterocyclic complexes 4b-d. The structure of complex 4b was fully illuminated by X-ray crystallography. The steric environment of these chiral ruthenium complexes 4b-d was evaluated in asymmetric transfer hydrogenation (ATH) of prochiral ketones in the presence of NaOiPr by using 2-propanol as the hydrogen source and solvent. The resultant catalytic system can achieve very good enantioselectivities (up to 91%) and high yields (up to 99%).
Kucukturkmen, Cigdem,Agac, Ahmet,Eren, Aysel,Karakaya, Idris,Aslantas, Mehmet,Celik, Omer,Ulukanli, Sabri,Karabuga, Semistan
p. 122 - 125
(2015/12/01)

Asymmetric transfer hydrogenation of alkyl/aryl or alkyl/methyl ketones catalyzed by known C2-symmetric ferrocenyl-based chiral bis(phosphinite)-Ru(II), Rh(I) and Ir(III) complexes
Known Ru(II), Rh(I) and Ir(III) complexes of C2-symmetric ferrocenyl based chiral bis(phoshinite) ligands were catalyzed the asymmetric transfer hydrogenation of alkyl/aryl or alkyl methyl ketones. Corresponding secondary alcohols were obtained with high enantioselectivities up to 98% ee and reactivities using iso-propanol as the hydrogen source.
Durap, Feyyaz,Karaka?, Duygu Elma,Ak, Bünyamin,Baysal, Akin,Aydemir, Murat
p. 92 - 97
(2016/07/06)

Enantioselective transfer hydrogenation of various ketones with novel efficient iridium(III) ferrocenyl-phosphinite catalysts
The asymmetric reduction of prochiral ketones is a pivotal reaction for the preparation of chiral alcohols which form an extremely important class of intermediates for fine chemicals and pharmaceuticals. Especially, iridium-based asymmetric reduction of ketones to enantiomerically enriched alcohols has recently attracted important attention by a number of research groups and interest in this area is growing. Therefore, a series of novel neutral mononuclear iridium(III) ferrocenyl-phosphinite complexes have been prepared and applied in the iridium(III)-catalyzed asymmetric transfer hydrogenation (ATH) of ketones to give corresponding secondary alcohols with outstanding enantioselectivities and reactivities using 2-propanol as the hydrogen source (up to 99% ee and 99% conversion). It was seen that the substituents on the backbone of the ligands resulted in a significant effect on both the activity and % enantioselectivity. Furthermore, the structural elucidation of the complexes was carried out by elemental analysis, IR and multi-nuclear NMR spectroscopic data.
Meri?, Nermin,Aydemir, Murat
p. 120 - 128
(2016/07/13)

Synthesis of aminomethyl quinazoline based ruthenium (II) complex and its application in asymmetric transfer hydrogenation under mild conditions
The new chiral aminomethyl quinazoline (amq) type ligand derived from L-phenylalanine was synthesized and coordinated with [RuCl2(PPh3)dppb] to obtain ruthenium(II) complex. This catalyst displayed considerable reactivity (up to 97% ee and 99% conversion) in the asymmetric transfer hydrogenation of ketones using 2-propanol as a hydrogen source in the presence of NaOiPr.
Agac, Ahmet,Karakaya, Idris,Sahin, Irfan,Emir, Sedat,Karabuga, Semistan,Ulukanli, Sabri
p. 189 - 193
(2016/07/25)

Enzymatic kinetic resolution of aliphatic sec-alcohols by LipG9, a metagenomic lipase
Bioprospection for new enantioselective enzymes for application in organic synthesis is a prominent area of investigation in biocatalysis. In this context, here we present the evaluation of an immobilized lipase isolated from a metagenomic library (LipG9) for the enzymatic kinetic resolution (EKR) of aliphatic sec-alcohols, which are still challenging substrates, since low enantioselectivity values are usually observed for these resolutions. LipG9 was successfully employed in EKR of aliphatic alcohols, which were resolved with satisfactory conversions (19-59%) and enantiomeric excesses for alcohols (26-88%) and esters (30-96%) by transesterification reactions, demonstrating that its performance is equal to or better than commercially available enzymes for the same reaction.
Bandeira, Pamela T.,Alnoch, Robson C.,De Oliveira, Alfredo R.M.,De Souza, Emanuel M.,De O.P., Fábio,Krieger, Nadia,Piovan, Leandro
p. 58 - 63
(2016/01/30)

Syntheses of enantiopure aliphatic secondary alcohols and acetates by bioresolution with lipase B from candida antarctica
The lipase B from Candida antarctica (Novozym 435, CALB) efficiently catalyzed the kinetic resolution of some aliphatic secondary alcohols: (±)-4-methylpentan- 2-ol (1), (±)-5-methylhexan-2-ol (3), (±)-octan-2-ol (4), (±)-heptan-3-ol (5) and (±)-oct-1- en-3-ol (6). The lipase showed excellent enantioselectivities in the transesterifications of racemic aliphatic secondary alcohols producing the enantiopure alcohols (>99% ee) and acetates (>99% ee) with good yields. Kinetic resolution of rac-alcohols was successfully achieved with CALB lipase using simple conditions, vinyl acetate as acylating agent, and hexane as non-polar solvent.
Ferreira, Hercules V.,Rocha, Lenilson C.,Severino, Richele P.,Porto, Andre L. M.
p. 8955 - 8967,13
(2020/08/31)

Chiral ligand derived from (1S,2R)-norephedrine as a catalyst for enantioselective prochiral ketone reduction
Chiral oxazaborolidines derived from (1S,2R)-(+)-norephedrine and substituted salicylaldehydes were employed in the asymmetric reduction of prochiral ketones using borane dimethyl sulfide as a reducing agent. The secondary alcohols were formed in excellent yields (45-99.8%) with enantioselectivities up to 99.8%. The effect of the substitution in the aromatic ring of the ligand was discussed with the enantioselectivity of the product.
Balakrishnan, Umesh,Ananthi, Nallamuthu,Velmathi, Sivan
experimental part
p. 1150 - 1153
(2009/09/27)

Enantioselective reduction of aliphatic ketones using oxazaborolidine catalyst generated in situ from chiral lactam alcohol and phenoxyborane
Oxazaborolidine catalyst generated in situ from chiral lactam alcohol 3 and p-iodophenoxyborane at room temperature was found to catalyze the enantioselective borane reduction of various prochiral aliphatic ketones at -20 °C with high enantioselectivity up to 98% ee. Copyright
Kawanami, Yasuhiro,Mikami, Yudai,Hoshino, Katsuhiro,Suzue, Mikiko,Kajihara, Izumi
supporting information; experimental part
p. 722 - 723
(2011/04/21)

Enzymatic process for the preparation of optically active alcohols from ketones using tuberous root Daucus carota
The present invention relates to an enzymatic process for the preparation of optically active chiral alcohols using tuberous root Daucus carota; particularly invention relates to an enzymatic process for the preparation of optically active alcohols by enantioselective reduction of corresponding ketones using tuberous root Daucus carota.
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(2008/06/13)

An efficient catalyst system for the asymmetric transfer hydrogenation of ketones: Remarkably broad substrate scope
A BINOL-derived diphosphonite having a xanthene backbone is an excellent bidentate ligand in Ru-catalyzed 2-propanol-based transfer hydrogenation of aryl/alkyl and alkyl/alkyl ketones (ee = 76-99%). Even notoriously difficult ketones such as isopropyl methyl ketone are reduced with extraordinarily high enantioselectivity (ee = 99%). Copyright
Reetz, Manfred T.,Li, Xiaoguang
p. 1044 - 1045
(2007/10/03)

Remarkably stable (Me3Al)2·DABCO and stereoselective nickel-catalyzed AlR3 (R = Me, Et) additions to aldehydes
(Chemical Equation Presented) Weigh it out in air! The DABAL reagent (Me3Al)2·(DABCO) (DABCO = 1,4-diazabicyclo[2.2.2] octane) can be easily handled under normal laboratory conditions. Furthermore, chiral secondary alcohols can be efficiently prepared from prochiral aldehydes (see scheme; TOF = turnover frequency) by using either DABAL or AIR3 reagents (R = Me, Et). Thus, DABAL can be used as an efficient, convenient alternative to the Schumann-Blum reagent.
Biswas, Kallolmay,Prieto, Oscar,Goldsmith, Paul J.,Woodward, Simon
p. 2232 - 2234
(2007/10/03)

Efficient enantioselective reduction of ketones with Daucus carota root
A novel and efficient reduction of various prochiral ketones such as acetopehones, α-azido aryl ketones, β-ketoesters, and aliphatic acyclic and cyclic ketones to the corresponding optically acive secondary alcohols with moderate to excellent chemical yield was achieved by using Daucus carota, root plant cells under extremely mild and environmentally benign conditions in aqueous medium, has been described. Many of these optically active alcohols are the potential chiral building blocks for the synthesis of pharmaceutically important molecules and asymmetric chiral ligands. Hence, this biocatalytic approach is found to be the most suitable for the preparation of a wide range of chiral alcohols and gave inspiration for the development of a new biotechnological process.
Yadav,Nanda,Thirupathi Reddy,Bhaskar Rao
p. 3900 - 3903
(2007/10/03)

Chirally modified NaBH4/ZrCl4 promoted asymmetric reduction of prochiral ketones
Enantioselective reduction of prochiral ketones has been achieved by the combination of NaBH4/ZrCl4 and (S)(-)-α,α-diphenyl prolinol in moderate to high enantiomeric excess.
Chary,Thomas,Iyengar
p. 57 - 59
(2007/10/03)

Asymmetric reduction of ketones by Geotrichum candidum in the presence of Amberlite Xad, A solid organic solvent
Asymmetric reduction of ketones by Geotrichum candidum in the presence of Amberlite XAD, a solid organic solvent, was described. A hydrophobic polymer, XAD, was used as material to control the stereochemical course of microbial reductions. Aliphatic and aromatic ketones were reduced to the corresponding (S)-alcohols in excellent enantiomeric excess (ee) in the presence of XRD while low enantioselectivities were observed in the absence of the polymer.
Nakamura, Kaoru,Fujii, Mikio,Ida, Yoshiteru
p. 3205 - 3211
(2007/10/03)

Highly enantioselective hydrogenation of simple ketones catalyzed by a Rh-PennPhos complex
Even alkyl methyl ketones undergo asymmetric hydrogenation with high enantioselectivity when a rhodium complex of the conformationally rigid chiral ligand 1 (Me-PennPhos; R = CH3) is used as the catalyst. Basic additives such as 2,6-lutidine contribute to the achievement of high enantiomeric excesses.
Jiang, Qiongzhong,Jiang, Yutong,Xiao, Dengming,Cao, Ping,Zhang, Xumu
p. 1100 - 1103
(2007/10/03)

Potential application of Sulfolobus solfataricus as catalyst in organic synthesis
Sulfolobus solfataricus, a thermoacidophilic archaeon, has been utilized as catalyst for several enzymatic transformations such as carbonyl-alcohol oxidoreductions, synthesis of glycosides, kinetic resolution of aminoacid esters, etc.All these reactions have been carried out at 75 deg C in accordance with the thermophilic nature of the enzymes present in the organisms.
Trincone, Antonio,Nicolaus, Barbara,Lama, Licia,Gambacorta, Agata
p. 25 - 29
(2007/10/02)

NEW CHIRAL BOROHYDRIDES. 3. PREPARATION AND ASYMMETRIC REDUCING PROPERTIES OF POTASSIUM 9-0 -(1,2-ISOPROPYLIDENE-5-DEOXY-α-D-XYLOFURANOSYL)-9-BORATABICYCLONONANE
A stable, new chiral borohydride, potassium 9-O- (1,2-O-isopropylidene-5-deoxy-α-D-xylofuranosyl)-9-boratabicyclononane (K xylide, 1D) using a xylose derivative as a chiral auxiliary was prepared by the treatment of the corresponding borinic ester 3D with potassium hydride in THF.The reagent provided high optical induction for asymmetric reduction of prochiral ketones, such as relatively hindered ketones, alkyl aromatic ketones, and α-haloketones.Thus, the reduction of 4-methyl-2-pentanone, 3,3-dimethyl-2-butanone, and 2,2-dimethylcyclopentanone provided thecorresponding alcohols in 65 percent ee, 76 percent ee, and 80 percent ee, respectively.The optical induction for unhindered aliphatic ketones was low, such as 36 percent for 2-heptanone, 46 percent ee for 3-methyl-2-butanone.The reductions of alkyl aromatic ketones provide high optical inductions, such as 70 percent ee for acetophenone, 82 percent ee for butyrophenone, 89 percent ee for isobutyrophenone, 99 percent ee for pivalophenone, and 93 percent ee for 2'-methylacetophenone.For some functionalized ketones, the reduction of 2-chloroacetophenone yields the corresponding alcohol in 92 percent ee, whereas the reduction of 3-acetylpyridine, methyl benzoylformate, and 4-phenyl-3-butyn-2-one provide the corresponding alcohols in 62 percent ee, 60 percent ee and 52 percent ee, respectively.
Cho, Byung Tae,Chun, Yu Sung
p. 73 - 84
(2007/10/02)

Asymmetric Hydride Reduction using a Chiral Aluminium Reagent Modified by a Crowned 2,2'-Dihydroxy-1,1'-binaphthyl
The chiral aluminium hydride reagent 6 modified by a crowned 2,2'-dihydroxy-1,1'-binaphthyl 4 was found to exhibit high enantiomeric face selectivity towards a variety of prochiral carbonyl compounds including aliphatic ketones.
Yamamoto, Koji,Ueno, Koji,Naemura, Koichiro
p. 2607 - 2608
(2007/10/02)

Organoboron Compounds in Organic Synthesis. 2. Asymmetric Reduction of Dialkyl Ketones with (R,R)- or (S,S)-2,5-Dimethylborolane
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Imai, Toshiro,Tamura, Tadashi,Yamamuro, Akira,Sato, Tsuneo,Wollmann, Theodor A.,et al.
p. 7402 - 7404
(2007/10/02)

Asymmetric Synthesis Using Chirally Modified Borohydrides. Part 3. Enantioselective Reduction of Ketones and Oxime Ethers with Reagents Prepared from Borane and Chiral Amino Alcohols
The asymmetric reduction of aromatic and aliphatic ketones, halogeno ketones, keto esters, and ketone oxime ethers with reagents prepared from borane and chiral amino alcohols has been investigated.When α,α-diphenyl-β-amino alcohols, such as (2S,3R)-(-)-2-amino-3-methyl-1,1-diphenylpentanol (2d), were used as a chiral auxiliary, very high enantioselectivities (ca. 90percent e.e.) were obtained in the reduction of various ketones and oxime ethers.
Itsuno, Shinichi,Nakano, Michio,Miyazaki, Koji,Masuda, Hirofumi,Ito, Koichi,et al.
p. 2039 - 2044
(2007/10/02)

ASYMMETRIC SYNTHESIS VIA CHIRAL SILICON REAGENTS. CHIRAL α-HYDROXYALKYL ANION EQUIVALENTS FROM VINYLSILANES CONTAINING OPTICALLY ACTIVE AMINO OR ALKOXY GROUPS ON SILICON
Chiral vinylsilanes containing optically active functional groups on silicon have been used as precursors for chiral α-hydroxyalkyl anion equivalents via a sequence of addition of n-butyllithium, coupling with organic halides, and oxidative cleavage of the silicon-carbon bond, to give optically active alcohols of up to 60percent ee.
Tamao, Kohei,Kanatani, Ryuichiro,Kumada, Makoto
p. 1913 - 1916
(2007/10/02)

Diastereoselective Reductions of β-Keto Sulfoximines
(S)-β-Keto sulfoximines have been prepared by butyllithium-mediated condensation of (+)-(S)-N,S-dimethyl-S-phenylsulfoximine with nitriles.The β-keto sulfoximines on treatment with a variety of reducing agents afforded β-hydroxy sulfoximines with varying diastereomeric ratios.Highest asymmetric inductions were observed with gaseous diborane.A sulfoximine-borane complex is suggested as an intermediate.Raney nickel desulfurization of the β-hydroxy sulfoximines afforded secondary alcohols with optical purities in the 18-69percent range.
Johnson, Carl R.,Stark, Charles J.
p. 1196 - 1200
(2007/10/02)

Hydroboartion. 62. Monoisopinocampheylborane, an Excellent Chiral Hydroborating Agent for Trans-Disubstituted and Trisubstituted Alkenes. Evidenece for a Strong Steric Dependence in Such Asymmetric Hydroborations
Monoisopinocampheylborane (IpcBH2), the first monoalkylborane chiral hydroborating agent, is capable of reacting with olefins of varying stuctural and steric requiments to produce, in most cases, clean dialkylboranes.IpcBH2 achieves the asymmetric hydroboration of trans-disubstituted and trisubstituted olefins with exceptionally high asymmetric induction.The product alcohols, produced by oxidation of the intermediate organoboranes, exhibit enantiomeric purities in the range of 53-100percent ee and reveal the same absolute configuration.Enantiomeric purities of the products increase with increasing steric requirements of the alkyl or phenyl substituent in the trans-disubstituted or trisubstituted alkene.
Brown, Herbert C.,Jadhav, Prabhakar K.,Mandal, Arun K.
p. 5074 - 5083
(2007/10/02)