共查询到20条相似文献,搜索用时 5 毫秒
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Dr. Johanna Novacek Joseph A. Izzo Prof. Dr. Mathew J. Vetticatt Prof. Dr. Mario Waser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17339-17344
Chiral bifunctional urea‐containing ammonium salts were found to be very efficient catalysts for asymmetric α‐hydroxylation reactions of β‐ketoesters with oxaziridines under base‐free conditions. The reaction is accompanied by a simultaneous kinetic resolution of the oxaziridine and a plausible and so far unprecedented bifunctional transition‐state model has been obtained by means of DFT calculations. 相似文献
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Kinetic Resolution of α‐Hydroxy‐Substituted Oxime Ethers by Enantioselective Cu−H‐Catalyzed Si−O Coupling 下载免费PDF全文
Xichang Dong Yuji Kita Prof. Dr. Martin Oestreich 《Angewandte Chemie (International ed. in English)》2018,57(33):10728-10731
A catalyst‐controlled enantioselective alcohol silylation by Cu?H‐catalyzed dehydrogenative Si?O coupling of hydroxy groups α to an oxime ether and simple hydrosilanes is reported. The selectivity factors reached in this kinetic resolution are generally high (s≈50), and these reactions thereby provide reliable access to highly enantioenriched α‐hydroxy‐substituted oxime ethers. The synthetic usefulness of these compounds is also demonstrated. 相似文献
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Z‐Selective Hydrothiolation of Racemic 1,3‐Disubstituted Allenes: An Atom‐Economic Rhodium‐Catalyzed Dynamic Kinetic Resolution 下载免费PDF全文
Adrian B. Pritzius Prof. Dr. Bernhard Breit 《Angewandte Chemie (International ed. in English)》2015,54(52):15818-15822
A Z‐selective rhodium‐catalyzed hydrothiolation of 1,3‐disubstituted allenes and subsequent oxidation towards the corresponding allylic sulfones is described. Using the bidentate 1,4‐bis(diphenylphosphino)butane (dppb) ligand, Z/E‐selectivities up to >99:1 were obtained. The highly atom‐economic desymmetrization reaction tolerates functionalized aromatic and aliphatic thiols. Additionally, a variety of symmetric internal allenes, as well as unsymmetrically disubstituted substrates were well tolerated, thus resulting in high regioselectivities. Starting from chiral but racemic 1,3‐disubstituted allenes a dynamic kinetic resolution (DKR) could be achieved by applying (S,S)‐Me‐DuPhos as the chiral ligand. The desired Z‐allylic sulfones were obtained in high yields and enantioselectivities up to 96 % ee. 相似文献
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Zhiyong Jiang Dr. Yuanyong Yang Yuanhang Pan Yujun Zhao Hongjun Liu Choon‐Hong Tan Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(19):4925-4930
Constructing α‐stereogenic amides and ketones : The highly regioselective and enantioselective conjugate addition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).
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Shen Qu Samuel M. Smith Víctor Laina‐Martín Rifahath M. Neyyappadath Mark D. Greenhalgh Andrew D. Smith 《Angewandte Chemie (International ed. in English)》2020,59(38):16572-16578
A highly enantioselective isothiourea‐catalyzed acylative kinetic resolution (KR) of acyclic tertiary alcohols has been developed. Selectivity factors of up to 200 were achieved for the KR of tertiary alcohols bearing an adjacent ester substituent, with both reaction conversion and enantioselectivity found to be sensitive to the steric and electronic environment at the stereogenic tertiary carbinol centre. For more sterically congested alcohols, the use of a recently‐developed isoselenourea catalyst was optimal, with equivalent enantioselectivity but higher conversion achieved in comparison to the isothiourea HyperBTM. Diastereomeric acylation transition state models are proposed to rationalize the origins of enantiodiscrimination in this process. This KR procedure was also translated to a continuous‐flow process using a polymer‐supported variant of the catalyst. 相似文献
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Efficient Synthesis of Differentiated syn‐1,2‐Diol Derivatives by Asymmetric Transfer Hydrogenation–Dynamic Kinetic Resolution of α‐Alkoxy‐Substituted β‐Ketoesters 下载免费PDF全文
Dr. Laure Monnereau Dr. Damien Cartigny Dr. Michelangelo Scalone Dr. Tahar Ayad Dr. Virginie Ratovelomanana‐Vidal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11799-11806
Asymmetric transfer hydrogenation was applied to a wide range of racemic aryl α‐alkoxy‐β‐ketoesters in the presence of well‐defined, commercially available, chiral catalyst RuII–(N‐p‐toluenesulfonyl‐1,2‐diphenylethylenediamine) and a 5:2 mixture of formic acid and triethylamine as the hydrogen source. Under these conditions, dynamic kinetic resolution was efficiently promoted to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters derived from substituted aromatic and heteroaromatic aldehydes with a high level of diastereoselectivity (diastereomeric ratio (d.r.)>99:1) and an almost perfect enantioselectivity (enantiomeric excess (ee)>99 %). Additionally, after extensive screening of the reaction conditions, the use of RuII‐ and RhIII‐tethered precatalysts extended this process to more‐challenging substrates that bore alkenyl‐, alkynyl‐, and alkyl substituents to provide the corresponding syn α‐alkoxy‐β‐hydroxyesters with excellent enantiocontrol (up to 99 % ee) and good to perfect diastereocontrol (d.r.>99:1). Lastly, the synthetic utility of the present protocol was demonstrated by application to the asymmetric synthesis of chiral ester ethyl (2S)‐2‐ethoxy‐3‐(4‐hydroxyphenyl)‐propanoate, which is an important pharmacophore in a number of peroxisome proliferator‐activated receptor α/γ dual agonist advanced drug candidates used for the treatment of type‐II diabetes. 相似文献
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Yujiro Hayashi Prof. Dr. Kazuki Obi Yusuke Ohta Daichi Okamura Hayato Ishikawa Dr. 《化学:亚洲杂志》2009,4(2):246-249
Direct and enantioselective : Diphenylprolinol silyl ether was found to catalyze the direct, asymmetric Michael reaction of 4‐substituted 2‐aryl‐2‐oxazoline‐5‐one and α,β‐unsaturated aldehydes, affording the chiral α,α‐disubstituted α‐amino acid derivatives with excellent enantioselectivity.
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Dynamic Kinetic Resolution of Heterobiaryl Ketones by Zinc‐Catalyzed Asymmetric Hydrosilylation 下载免费PDF全文
Dr. Valentín Hornillos José A. Carmona Dr. Abel Ros Dr. Javier Iglesias‐Sigüenza Dr. Joaquín López‐Serrano Prof. Rosario Fernández Prof. José M. Lassaletta 《Angewandte Chemie (International ed. in English)》2018,57(14):3777-3781
A diastereo‐ and highly enantioselective dynamic kinetic resolution (DKR) of configurationally labile heterobiaryl ketones is described. The DKR proceeds by zinc‐catalyzed hydrosilylation of the carbonyl group, thus leading to secondary alcohols bearing axial and central chirality. The strategy relies on the labilization of the stereogenic axis that takes place thanks to a Lewis acid–base interaction between a nitrogen atom in the heterocycle and the ketone carbonyl group. The synthetic utility of the methodology is demonstrated through stereospecific transformations into either N,N‐ligands or appealing axially chiral, bifunctional thiourea organocatalysts. 相似文献
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Enzyme‐ and Ruthenium‐Catalyzed Enantioselective Transformation of α‐Allenic Alcohols into 2,3‐Dihydrofurans 下载免费PDF全文
Bin Yang Dr. Can Zhu Dr. Youai Qiu Prof. Dr. Jan‐E. Bäckvall 《Angewandte Chemie (International ed. in English)》2016,55(18):5568-5572
An efficient one‐pot method for the enzyme‐ and ruthenium‐catalyzed enantioselective transformation of α‐allenic alcohols into 2,3‐dihydrofurans has been developed. The method involves an enzymatic kinetic resolution and a subsequent ruthenium‐catalyzed cycloisomerization, which provides 2,3‐dihydrofurans with excellent enantioselectivity (up to >99 % ee). A ruthenium carbene species was proposed as a key intermediate in the cycloisomerization. 相似文献
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Connor J. Thomson David M. Barber Darren J. Dixon 《Angewandte Chemie (International ed. in English)》2020,59(13):5359-5364
The catalytic enantioselective synthesis of α‐fluorinated chiral tertiary alcohols from (hetero)aryl methyl ketones is described. The use of a bifunctional iminophosphorane (BIMP) superbase was found to facilitate direct aldol addition by providing the strong Brønsted basicity required for rapid aryl enolate formation. The new synthetic protocol is easy to perform and tolerates a broad range of functionalities and heterocycles with high enantioselectivity (up to >99:1 e.r.). Multi‐gram scalability has been demonstrated along with catalyst recovery and recycling. 1H NMR studies identified a 1400‐fold rate enhancement under BIMP catalysis, compared to the prior state‐of‐the‐art catalytic system. The utility of the aldol products has been highlighted with the synthesis of various enantioenriched building blocks and heterocycles, including 1,3‐aminoalcohol, 1,3‐diol, oxetane, and isoxazoline derivatives. 相似文献
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Stereoarrayed CF3‐Substituted 1,3‐Diols by Dynamic Kinetic Resolution: Ruthenium(II)‐Catalyzed Asymmetric Transfer Hydrogenation 下载免费PDF全文
Andrej Emanuel Cotman Dr. Dominique Cahard Dr. Barbara Mohar 《Angewandte Chemie (International ed. in English)》2016,55(17):5294-5298
CF3‐substituted 1,3‐diols were stereoselectively prepared in excellent enantiopurity and high yield from CF3‐substituted diketones by using an ansa‐ruthenium(II)‐catalyzed asymmetric transfer hydrogenation in formic acid/triethylamine. The intermediate mono‐reduced alcohol was also obtained in very high enantiopurity by applying milder reaction conditions. In particular, CF3C(O)‐substituted benzofused cyclic ketones underwent either a single or a double dynamic kinetic resolution during their reduction. 相似文献
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