Synthesis Of Chiral Allylic Alcohols Research Articles

Stabilization of α-ZrP ceramic nanosheets adsorbing quaternary ammonium ions in organic solvents and their application as a stable solid support for lipase catalyzing stereospecific synthetic reactions

ABSTRACT Herein, the effect of immobilizing lipase onto layered α-zirconium phosphate ceramic nanosheets (α-ZrP NS) on the enzymatic transesterification of allylic alcohols was investigated in organic solvents. α-ZrP NS modified with quaternary ammonium ions show a excellent dispersion stability in n-hexane. Lipase immobilized on α-ZrP NS enables the improved synthesis of chiral allylic alcohols and esters, with significantly reduced reaction times compared to reactions performed in the absence of α-ZrP NS. The coexistence of α-ZrP NS also results in more efficient steric inversion of the resulting allyl ester, suggesting the utility of α-ZrP NS as a support for lipase-induced stereospecific reactions. The present manuscript discusses on mechanisms of high dispersion stability of α-ZrP NS and their preferable immobilizing effect for the lipase inducing the steric inversion in detail.

ChemInform Abstract: An Oxazaborolidine‐Based Catalytic Method for the Asymmetric Synthesis of Chiral Allylic Alcohols.

Abstract The enantioselective reduction of a broad range of prochiral α,β-unsaturated ketones 1a – 1y using the oxazaborolidine-based catalyst providing chiral allylic alcohols 2a – 2y with both high enantioselectivity and chemoselectivity is described. The optimum reaction conditions were found using the oxazaborolidine catalysts prepared in situ from the chiral amino alcohols and borane reagents. Various chiral amino alcohols 4a – 4f were screened for this one-pot asymmetric reduction of α,β-enones. Amino alcohol 4a [( R )-DPP] and trimethylboroxine catalyze this asymmetric reduction in toluene at −20 °C within 0.5–2 h in a highly efficient manner. The synthesized chiral allylic alcohols 2a – 2y are new compounds, which are valuable intermediates in the preparation of new ligands and in the synthesis of several natural molecules.

An oxazaborolidine-based catalytic method for the asymmetric synthesis of chiral allylic alcohols

The enantioselective reduction of a broad range of prochiral α,β-unsaturated ketones 1a–1y using the oxazaborolidine-based catalyst providing chiral allylic alcohols 2a–2y with both high enantioselectivity and chemoselectivity is described. The optimum reaction conditions were found using the oxazaborolidine catalysts prepared in situ from the chiral amino alcohols and borane reagents. Various chiral amino alcohols 4a–4f were screened for this one-pot asymmetric reduction of α,β-enones. Amino alcohol 4a [(R)-DPP] and trimethylboroxine catalyze this asymmetric reduction in toluene at −20°C within 0.5–2h in a highly efficient manner. The synthesized chiral allylic alcohols 2a–2y are new compounds, which are valuable intermediates in the preparation of new ligands and in the synthesis of several natural molecules.

ChemInform Abstract: Ruthenium‐Catalyzed Regio‐ and Enantioselective Allylic Substitution with Water: Direct Synthesis of Chiral Allylic Alcohols.

AbstractThe simplicity and availability of the nucleophile, the mild conditions, and the broad scope of the allylic chlorides are features of the present reaction.

Ruthenium‐Catalyzed Regio‐ and Enantioselective Allylic Substitution with Water: Direct Synthesis of Chiral Allylic Alcohols

Weniger ist mehr: Ein neuer Zugang zu chiralen Allylalkoholen nutzt die regio- und enantioselektive Substitutionsreaktion monosubstituierter Allylchloride mit Wasser. Die Reaktion wird von planar-chiralen Cyclopentadienylrutheniumkomplexen effizient katalysiert (siehe Schema). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. 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.

Ruthenium‐Catalyzed Regio‐ and Enantioselective Allylic Substitution with Water: Direct Synthesis of Chiral Allylic Alcohols

Enantioselective allylic substitution catalyzed by transitionmetal complexes is an important process in organic synthesis. For many years, mainly palladium complexes that contain chiral ligands have been employed as efficient catalysts in these reactions. Recent studies have demonstrated that chiral catalysts based on other transition metals show different regioselectivity in the synthesis of branched allylic products via monosubstituted p-allyl intermediates. Although a variety of carbon and nitrogen nucleophiles can be used in those reactions, applicable oxygen nucleophiles are still limited to phenols and alcohols, which produce allylic ethers. Thus, enantioenriched branched allylic alcohols, which serve as useful chiral building blocks, are often synthesized by other processes, such as the hydrogenation of a,b-unsaturated ketones, the nucleophilic addition of vinylmetal reagents to aldehydes and ketones, and the kinetic resolution of racemic allylic alcohols. Recently, new ways to access these compounds have been developed, and they involve allylic substitution by a two-step conversion involving allylic esters and silyl ethers (Scheme 1; OPG= ester or silyl

ChemInform Abstract: Nickel‐Catalyzed Enantioselective Alkylative Coupling of Alkynes and Aldehydes: Synthesis of Chiral Allylic Alcohols with Tetrasubstituted Olefins.

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 of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Nickel-Catalyzed Enantioselective Alkylative Coupling of Alkynes and Aldehydes: Synthesis of Chiral Allylic Alcohols with Tetrasubstituted Olefins

A highly efficient nickel-catalyzed asymmetric alkylative coupling of alkynes, aldehydes, and dimethylzinc has been realized by using bulky spirobiindane phosphoramidite ligands, affording allylic alcohols with a tetrasubstituted olefin functionality in high yields, high regioselectivities, and excellent enantioselectivities.

ChemInform Abstract: A Highly Enantioselective Synthesis of Chiral Allylic Alcohols by Asymmetric Addition of Novel Mixed Reagents of Trialkenylbismuthines/Dialkylzincs to Aldehydes.

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 of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A highly enantioselective synthesis of chiral allylic alcohols by asymmetric addition of novel mixed reagents of trialkenylbismuthines/dialkylzincs to aldehydes

A novel mixture of reagents of trialkenylbismuthines/dialkylzincs was developed and applied toward the synthesis of chiral allylic alcohols. The chiral β-amino alcohols catalyzed addition of the mixed reagents of trialkenylbismuthines/dialkylzincs to aldehydes gave enantiomerically enriched allylic alcohols with up to 97% ee.

Ultrasound‐Accelerated Synthesis of Chiral Allylic Alcohols Promoted by Indium Metal.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Ultrasound-accelerated synthesis of chiral allylic alcohols promoted by indium metal

The 2-iodomethyl- O-isopropylidine acetals undergo smoothly β-elimination by indium metal in methanol under sonication to afford the corresponding allylic alcohols in excellent yields with high selectivity. This method tolerates both acid and base labile functional and protecting groups and also free hydroxyl groups present in the molecule. Improved yields and enhanced rates are the remarkable features obtained by ultrasound.

Composition of the activated complex in the stereoselective deprotonation of cyclohexene oxide by a chiral lithium amide

Chiral lithium amides are being developed for stereoselective synthesis of chiral allylic alcohols in high yields and with high enantiomeric excess. However, rational design of the amides for improved stereoselectivity by computational methods, for example, has not been possible due to lack of knowledge of the activated complexes involved in the reactions. Kinetic results are presented for the stereoselective deprotonation by lithium ( S)-1-(2-pyrrolidinylmethyl)pyrrolidide ( 1-Li) of cyclohexene oxide 2, in diethyl ether (DEE), to form ( S)-2-cyclohexen-1-ol ( S)- 3 in high enantiomeric excess. The results show that the rate limiting activated complex is composed of one lithium amide monomer and one molecule of 2 and presumably a solvent molecule. The diamine 1 is found to catalyze the deprotonation.

ChemInform Abstract: Synthesis of Chiral Allylic Alcohols by the Reaction of Chiral Titanium‐Alkyne Complexes with Carbonyl Compounds.

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.

Synthesis of chiral allylic alcohols by the reaction of chiral titanium–alkyne complexes with carbonyl compounds

Chiral titanium–alkyne complexes derived from chlorotris[(–)-menthoxy]titanium/2 PriMgCl and alkynes react with aldehydes to afford optically active allylic alcohols in up to 38% ee.