Dynamic Kinetic Resolution Of Alcohols Research Articles

Lipase/H2SO4‐Cocatalyzed Dynamic Kinetic Resolution of Alcohols in Pickering Emulsion

AbstractThis study reports the first chemoenzymatic dynamic kinetic resolution (DKR) of racemic sec‐alcohols by simultaneously using immobilized lipase and aqueous sulfuric acid as catalysts for kinetic resolution and racemization, respectively. The nanoparticle‐stabilized phase separation in a Pickering emulsion enabled the use of these inherently incompatible catalysts in a single vessel. The racemization reaction in the aqueous sulfuric acid solution significantly suppressed the dehydrative side reactions that form alkenes and dimeric ethers, which are often observed in racemization using Brønsted/Lewis acids or oxovanadium compounds in organic solvents. The efficacy of the Pickering emulsion was confirmed by the significantly lower catalytic performance in DKR without emulsification. This method achieved high yields and high optical purities in the production of a wide range of sec‐alcohols.

Progress on the Stereoselective Synthesis of Chiral Molecules Based on Metal-Catalyzed Dynamic Kinetic Resolution of Alcohols with Lipases

Metal/lipase-combo catalyzed dynamic kinetic resolution (DKR) of racemic chiral alcohols is a general and practical process to obtain the corresponding enantiopure esters R with quantitative conversion. The use of known Ru-catalysts as well as newly developed homogeneous and heterogeneous metal catalysts (Fe, V) contributed to make the DKR process more sustainable and to expand the substrate scope of the reaction. In addition to classical substrates, challenging allylic alcohols, tertiary alcohols, C1-and C2-symmetric biaryl diols turned out to be competent substrates. Synthetic utility further emerged from the integration of this methodology into cascade reactions leading to linear/cyclic chiral molecules with high ee through the formation of multiple bonds, in a one-pot procedure.

Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts.

A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition‐metal‐catalyzed alcohol racemization and enantioselective Cu‐H‐catalyzed dehydrogenative Si‐O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often‐used ruthenium half‐sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.

Lipase-catalyzed asymmetric synthesis of naphtho[2,3-c]furan-1(3H)-one derivatives by a one-pot dynamic kinetic resolution/intramolecular Diels–Alder reaction: Total synthesis of (−)-himbacine

One-pot sequential reactions using the acyl moieties installed by enzymatic dynamic kinetic resolution of alcohols have been little investigated. In this work, the acryloyl moiety installed via the lipase/oxovanadium combo-catalyzed dynamic kinetic resolution of a racemic dienol [4-(cyclohex-1-en-1-yl)but-3-en-2-ol or 1-(cyclohex-1-en-1-yl)but-2-en-1-ol] with a (Z)-3-(phenylsulfonyl)acrylate underwent an intramolecular Diels–Alder reaction in a one-pot procedure to produce an optically active naphtho[2,3-c]furan-1(3H)-one derivative (98% ee). This method was successfully applied to the asymmetric total synthesis of (−)-himbacine.

Combinatorial library based engineering of Candida antarctica lipase A for enantioselective transacylation of sec-alcohols in organic solvent.

A method for determining lipase enantioselectivity in the transacylation of sec-alcohols in organic solvent was developed. The method was applied to a model library of Candida antarctica lipase A (CalA) variants for improved enantioselectivity (E values) in the kinetic resolution of 1-phenylethanol in isooctane. A focused combinatorial gene library simultaneously targeting seven positions in the enzyme active site was designed. Enzyme variants were immobilized on nickel-coated 96-well microtiter plates through a histidine tag (His6-tag), screened for transacylation of 1-phenylethanol in isooctane, and analyzed by GC. The highest enantioselectivity was shown by the double mutant Y93L/L367I. This enzyme variant gave an E value of 100 (R), which is a dramatic improvement on the wild-type CalA (E=3). This variant also showed high to excellent enantioselectivity for other secondary alcohols tested.

Ligand effect in racemization and dynamic kinetic resolution of alcohols: Mechanism on cymene ruthenium complexes

A family of ruthenium complexes with different ligands was utilized in racemization of (R)-1-phenylethanol to investigate the potential influence of the ligands coordinated to the ruthenium center. Kinetic experiments showed that 16-electron cymene ruthenium complex with two chloro-bridge bonds and 18-electron ones with easily dissociative ligands are highly active for catalytic racemization of alcohols. Possible racemization mechanism for cymene ruthenium complexes was then proposed. Computational analysis of dissociation energy barrier, NBO analysis and reaction potential energy surface suggest that ligand-dissociation process is the vital step of the racemization catalyzed by cymene ruthenium complexes. Thereafter, these complexes were applied in the DKR of secondary alcohols to verify their efficiency and applicability.

ChemInform Abstract: Highly Efficient Dynamic Kinetic Resolution of Secondary Aromatic Alcohols Using a Low‐Cost Solid Super Acid as a Racemization Catalyst.

AbstractThe dynamic kinetic resolution of alcohols (I) with 4‐chlorophenyl valerate as acyl donor proceeds in the presence of Novozym 435 and sulfated TiO2 as nano solid super acidic racemization catalyst.

ChemInform Abstract: Enantioselective Route to Ketones and Lactones from Exocyclic Allylic Alcohols via Metal and Enzyme Catalysis.

AbstractThe key steps of the procedure are dynamic kinetic resolution of alcohols (I) and regio‐ and stereoselective substitution of the acetates (III).

ChemInform Abstract: Chemoenzymatic Dynamic Kinetic Resolution of Alcohols and Amines

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.

Chemoenzymatic Dynamic Kinetic Resolution of Alcohols and Amines

AbstractDynamic kinetic resolution (DKR) is an attractive process for the transformation of racemic mixtures into optically active compounds. For successful DKR, efficient racemization is required while the kinetic resolution is proceeding. This Microreview mainly summarizes the recent developments in the DKR of alcohols and amines, based on metal‐catalyzed racemization and enzymatic acylation in a single reaction vessel. Related reactions involving precursors of alcohols and amines such as ketones, enol acetates, and ketoximes are also described. Reaction conditions are arranged according to racemization catalysts, and substrates employed in the DKR are tabulated. Suggested mechanisms for metal‐catalyzed racemizations are also summarized.

Ruthenium and enzyme-catalyzed dynamic kinetic resolution of alcohols

Abstract Ruthenium acts as a good catalyst for the racemization reaction of secondary alcohols and amines. Ruthenium-catalyzed racemization is coupled with enzymatic kinetic resolution to prepare chiral compounds in 100% theoretical yield. Ten ruthenium complexes ( 1 – 10 ) act as a good catalyst the for racemization reaction and are also compatible with DKR process. Two other ruthenium complexes [RuCl 2 (PPh 3 ) 3 ] and [Cp ∗ RuCl(COD)] are active for racemization reaction but their successful compatibility with DKR has not yet been reported. Ru/γ-Al 2 O 3 and Ru–HAP are the heterogeneous catalysts used for the racemization reaction. They have also not been employed for DKR process. Polymer supported ruthenium is employed as a reusable racemization catalyst for aerobic DKR of alcohols.

Dynamic Kinetic Resolution of Alcohols by a Racemization Catalyst and a Lipase

Dynamic Kinetic Resolution of Alcohols by a Racemization Catalyst and a Lipase

Highly Compatible Metal and Enzyme Catalysts for Efficient Dynamic Kinetic Resolution of Alcohols at Ambient Temperature.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly Compatible Metal and Enzyme Catalysts for Efficient Dynamic Kinetic Resolution of Alcohols at Ambient Temperature

Highly compatible metal and enzyme catalysts for efficient dynamic kinetic resolution of alcohols at ambient temperature

Highly Compatible Metal and Enzyme Catalysts for Efficient Dynamic Kinetic Resolution of Alcohols at Ambient Temperature

Sehr kurze Reaktionszeiten bei Raumtemperatur: Die Kombination hochkompatibler Metall- und Enzymkatalysatoren ermöglichte die schnellste jemals beschriebene dynamische kinetische Racematspaltung bei Alkoholen. Mit dem Rutheniumkatalysator 1 a (oder 1 b) und einer immobilisierten Lipase gelang bei Raumtemperatur und in ausgezeichneter Ausbeute die effiziente enantioselektive Synthese von Acetaten (siehe Schema). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2004/z461416_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.