1117-61-9Relevant articles and documents
A re-examination of pressure effects on enantioselectivity in asymmetric catalytic hydrogenation
Sun,Landau,Wang,LeBlond,Blackmond
, p. 1348 - 1353 (1996)
Marked shifts in enantioselectivity in the asymmetric hydrogenation of several prochiral substrates were observed as a function of the availability of hydrogen to the catalyst in both heterogeneous and homogeneous catalytic reactions. The key kinetic parameter affecting enantioselectivity was found to be concentration of molecular hydrogen in the liquid phase, [H2], rather than hydrogen pressure in the gas phase, and it was observed that under typical reaction conditions, [H2] could differ widely from its equilibrium saturation value. It was demonstrated that the reported pressure dependence on enantioselectivity may in fact be reproduced at constant pressure for several systems by varying the rate of gas-liquid mass transfer. The general significance of the conclusions suggest that considerations of hydrogen diffusion limitations might be important in other asymmetric hydrogenation studies reported in the literature. For systems where enantioselectivity depends positively on hydrogen pressure, the intrinsic ability of a catalyst to effect asymmetric hydrogenation may be masked in a reaction carried out under conditions where gas-liquid diffusion is the rate-limiting step.
Lipase-catalysed transesterification using 2,2,2-trifluoroethyl butyrate: Effect of temperature on rate of reaction and enantioselectivity
Parmar,Prasad,Singh,Gupta
, p. 1395 - 1398 (1992)
Temperature of the reaction and the solvent used markedly influenced the enantioselectivity and rate of transesterification reaction catalysed by Candida cylindracea between 2,2,2-trifluoroethyl butyrate (TFEB) and 3,7-dimethyl-6-octenol, and that between TFEB and 2,2-dimethyl-1,3-dioxolane-4-methanol.
Chemoselective transfer hydrogenation of aldehydes in aqueous media catalyzed by a well-defined iron(II) hydride complex
Gorgas, Nikolaus,Ilic, Aleksandra,Kirchner, Karl
, p. 121 - 126 (2019)
Abstract: An iron(II) hydride PNP pincer complex is applied as catalyst for the chemoselective transfer hydrogenation of aldehydes using an aqueous solution of sodium formate as hydrogen source. A variety of aromatic, heteroaromatic, and aliphatic aldehydes could be reduced to the corresponding alcohols in good to excellent yields with a catalyst loading of 1.0?mol% at 80?°C and 1?h reaction time. If present, C–C double bonds remained unaffected in course of the reaction, even when they are conjugated to the carbonyl group of the aldehyde. The catalyst’s lifetime and activity could be improved when the reactions were conducted in an ionic liquid-based micro emulsion. Graphical abstract: [Figure not available: see fulltext.].
Preparative Production of Optically Active Esters and Alcohols Using Esterase-Catalyzed Stereospecific Transesterification in Organic Media
Cambou, Bernard,Klibanov, Alexander M.
, p. 2687 - 2692 (1984)
A novel enzymatic approach to the production of optically active alcohols and esters from racemates is developed.It involves the use of esterase catalyzed transesterifications carried out in biphasic aqueous-organic mixtures.Water-insoluble substrates constitute the organic phase, while the enzyme is located in the aqueous phase.Since the fraction of the latter phase can be made very low, such an arrangement solves the problem of both the competition of an alcohol (the nucleophile) with water in the enzymatic reaction and poor solubility of most organic esters and alcohols in water.By use of porous supports (Sepharose or Chromosorb) filled with aqueous solutions of hog liver carboxyl esterase as a stereoselective catalyst and methyl propionate as a matrix ester, the following optically active alcohols and their propionic esters were produced on a preparative scale: 3-methoxy-1-butanol, 3-methyl-1-pentanol, 3,7-dimethyl-1-octanol, and β-citronellol.To overcome a rather narrow substrate specificity of hog liver carboxyl esterase, a nonspecific lipase from yeast (Candida cylindracea) also was employed as a stereoselective transesterification catalyst.Using an aqueous solution of this enzyme confined to the pores of Chromosorb and tributyrin as a matrix ester, we have prepared gram amounts of the following optically active alcohols and their butyric esters: 2-butanol, sec-phenethyl alcohol, 2-octanol, 1-chloro-2-propanol and 2,3-dichloro-1-propanol (subsequently nonenzymatically converted to optically active propylene oxide and epichlorohydrin, respectively), 6-methyl-5-hepten-2-ol, and 1,2-butanediol.
Application of Ring Closing Metathesis to the First Total Synthesis of (R)-(+)-Muscopyridine: Determination of Absolute Stereochemistry
Hagiwara, Hisahiro,Katsumi, Tomoko,Kamat, Vijayendra P.,Hoshi, Takashi,Suzuki, Toshio,Ando, Masayoshi
, p. 7231 - 7234 (2000)
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Enantioselectivity of the bioconversion of chiral citronellal during the inhibition of wheat seeds germination
Cavalieri, Andrea,Fischer, Ravit,Larkov, Olga,Dudai, Nativ
, p. 419 - 426 (2014)
Citronellal is one of the most prominent monoterpenes present in many essential oils. Low persistence of essential oils as bioherbicides has often been addressed because of the high volatility of these compounds. Bioconversion of citronellal by wheat seeds releases less aggressive and injurious compounds as demonstrated by their diminished germination. We demonstrated that optically pure citronellal enantiomers were reduced to optically pure citronellol enantiomers with retention of the configuration both in isolated wheat embryos and endosperms. Our findings reveal the potential of essential oils as allelopathic agents providing an insight into their mechanism of action and persistence. Copyright
The first stereoselective total synthesis of the immunosuppressive decalin derivative monascusic acid B 1
Kumar, Jayprakash Narayan,Das, Biswanath
, p. 863 - 865 (2014)
The first stereoselective total synthesis of the immunosuppressive decalin derivative monascusic acid B has been accomplished from (R)-(+)-pulegone involving Horner-Wadsworth-Emmons and Julia-Kocienski olefination reactions and Lewis acid catalyzed intramolecular Diels-Alder cyclization. Georg Thieme Verlag Stuttgart New York.
Furanoterpene synthesis via intramolecular nitrile oxide cycloaddition reaction: a total synthesis of (+)-menthofuran
Shishido, Kozo,Umimoto, Koji,Takata, Takeshi,Irie, Osamu,Shibuya, Masayuki
, p. 345 - 358 (1993)
A fused furan assembling strategy based on an intramolecular dipolar cycloaddition reaction of nitrile oxide has been applied to a total synthesis of perfumy furanomonoterpene (+)-menthofuran (1).The key cycloaddition substrates (9) and (12) are easily prepared via straightforward routes starting from (+)-citronellal and these are treated with sodium hypochlorite and p-chlorophenyl isocyanate, respectively.The cycloaddition reactions generate 10 : 1 mixture of diastereoisomeric isoxazolines (2a) and (2b) in good to excellent yields.The isoxazolines (2a,b)thus obtained are converted to (+)-menthofuran (1) by sequential reductive hydrolysis and alkaline hydrolysis (or vice versa) followed by acid treatment of the resulting β,γ-dihydroxy ketone (14).
Reduction of carbonyl compounds via hydrosilylation catalyzed by well-defined PNP-Mn(I) hydride complexes
Weber, Stefan,Iebed, Dina,Glatz, Mathias,Kirchner, Karl
, p. 635 - 639 (2021/06/17)
Reduction reactions of unsaturated compounds are fundamental transformations in synthetic chemistry. In this context, the reduction of polarized double bonds such as carbonyl or C=C motifs can be achieved by hydrogenation reactions. We describe here a highly chemoselective Mn(I)-based PNP pincer catalyst for the hydrosilylation of aldehydes and ketones employing polymethylhydrosiloxane (PMHS) as inexpensive hydrogen donor. Graphic abstract: [Figure not available: see fulltext.]
Sulfonic acid anchored on silica, SiO2@SO3H: A superior solid acid catalyst for quick and solvent-free reductive-deoxygenation of ketones with NaBH3CN
Zeynizadeh, Behzad,Kouhkan, Mehri
, p. 1521 - 1528 (2018/11/23)
NaBH3CN as a modified hydroborate agent and due to a strong withdrawing CN group does not show any reducing ability to reduce functional groups in the absence of acidic media (pH ~ 3–4). In this study, the immobilized sulfonic acid on silica, SiO2@SO3H, was prepared and applied as a new solid acid catalyst for extremely enhancing the reducing ability of NaBH3CN. The influence of SiO2@SO3H was highlighted by performing the quick and green reduction of structurally diverse carbonyl compounds involving aldehydes, ketones, α,β-unsaturated enals and enones, α-diketones, and acyloins to the corresponding alcohols or alkanes with NaBH3CN. By the NaBH3CN/SiO2@SO3H system, aldehydes were reduced to the corresponding alcohols and ketonic compounds to alkanes as reductive-deoxygenation products. All reduction reactions were carried out within 3 min at room temperature and under solvent-free conditions to afford the products in high to excellent yields (90–98%).
