نتایج جستجو برای: asymmetric catalyst

تعداد نتایج: 108514  

Journal: :Molecules 2017
Yi Li Qing-Zhu Li Li Huang Hong Liang Kai-Chuan Yang Hai-Jun Leng Yue Liu Xu-Dong Shen Xiao-Jun Gou Jun-Long Li

A highly diastereoselective cyclopropanation of cyclic enones with sulfur ylides was developed under catalyst-free conditions, producing multifunctional spirocyclopropanes in generally excellent yields (up to 99% yield and >99:1 d.r.). The asymmetric version of this method was realized by using an easily available chiral sulfur ylide, affording products with moderate to good stereoselectivity.

Journal: :Chemical communications 2010
Giulia Bergonzini Lucia Gramigna Andrea Mazzanti Mariafrancesca Fochi Luca Bernardi Alfredo Ricci

The asymmetric Povarov reaction of N-arylimines with 2- and 3-vinylindoles has been developed using a chiral phosphoric acid ((S)-TRIP) as catalyst. The peculiar reactivity of vinylindoles allowed also the disclosure of a Povarov Friedel-Crafts sequence, and the trapping of the reaction intermediate with nucleophilic species, thus providing a versatile platform for the preparation of highly ena...

Journal: :Chemical science 2017
Yang'en You Long Zhang Sanzhong Luo

A reagent-controlled enantioselectivity switch was uncovered in the asymmetric α-fluorination of β-ketocarbonyls by a chiral primary amine catalyst. By a simple swap of fluorination reagents, both enantiomers of the quaternary fluorination adducts could be obtained with good yields and high enantioselectivity. Mechanistic studies disclosed dual H-bonding and electrostatic stereocontrolling mode...

2015
Amparo Prades Maitane Fernández Sebastian D Pike Michael C Willis Andrew S Weller

A Rh-catalyst system based on the asymmetric ligand (t)Bu2PCH2P(o-C6H4OMe)2 is reported that allows for the hydroacylation of challenging internal alkenes with β-substituted aldehydes. Mechanistic studies point to the stabilizing role of both excess alkene and the OMe-group.

2016
Pierre Querard Inna Perepichka Eli Zysman-Colman Chao-Jun Li

This report describes a highly enantioselective oxidative sp3 C-H arylation of N-aryltetrahydroisoquinolines (THIQs) through a dual catalysis platform. The combination of the photoredox catalyst, [Ir(ppy)2(dtbbpy)]PF6, and chiral copper catalysts provide a mild and highly effective sp3 C-H asymmetric arylation of THIQs.

Journal: :Organic & biomolecular chemistry 2014
Buddhadeb Mondal Subhas Chandra Pan

Primary amino acids are found to be good enantioselective catalysts for the direct asymmetric Mannich reaction between 2-amino acetophenone and aldehydes. The 2-aryl-2,3-dihydro-4-quinoline products are obtained in moderate to good yields and good to high enantioselectivities with 10 mol% of the primary amino acid catalyst under mild reaction conditions.

Journal: :Journal of the American Chemical Society 2013
John Hartung Robert H Grubbs

The synthesis of a ruthenium complex that catalyzes Z-selective (up to 98% Z) asymmetric ring-opening/cross-metathesis with high enantioselectivity (up to 95% ee) is reported. The synthesis of the catalyst features the resolution of a chelating N-heterocyclic carbene complex by ligand substitution with a chiral carboxylate.

Journal: :Accounts of chemical research 2007
Adriaan J Minnaard Ben L Feringa Laurent Lefort Johannes G de Vries

Monodentate phosphoramidites are excellent ligands for Rh-catalyzed asymmetric hydrogenations of substituted olefins. Enantioselectivities between 95 and 99% were obtained in the asymmetric hydrogenation of protected alpha- and beta-dehydroamino acids and esters, itaconic acid and esters, aromatic enamides, aromatic enol esters, aromatic and aliphatic enol carbamates, and alpha-substituted cinn...

Journal: :Beilstein Journal of Organic Chemistry 2021

An organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones is reported. A bifunctional thiourea catalyst was found to be effective for this reaction. With 10 mol % of the catalyst, good results were attained a variety 1,5-dihydro-2 H -pyrrol-2-ones under mild conditions.

Journal: :Chemical communications 2007
Wei-Jun Tang Shou-Fei Zhu Li-Jin Xu Qi-Lin Zhou Qing-Hua Fan Hai-Feng Zhou Kimhung Lam Albert S C Chan

The chiral diphosphinite ligand derived from (R)-1,1'-spirobiindane-7,7'-diol has been found to be highly effective in the Ir-catalyzed asymmetric hydrogenation of quinolines with high substrate/catalyst ratio (up to 5000) and high enantioselectivity (up to 94% ee).

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