Enantioselective alkylation of β-keto esters promoted by dimeric Cinchona-derived ammonium salts as recoverable organocatalysts
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چکیده
منابع مشابه
Catalytic enantioselective fluorination of beta-keto esters by phase-transfer catalysis using chiral quaternary ammonium salts.
[reaction: see text] The catalytic enantioselective electrophilic fluorination promoted by quaternary ammonium salt from cinchonine as a phase-transfer catalyst is described. Treatment of beta-keto esters with N-fluorobenzenesulfonimide as the fluorine source under mild reaction conditions afforded the corresponding alpha-fluoro beta-keto esters in exellent yields with good to moderate enantiom...
متن کاملPolymer-supported Cinchona alkaloid-derived ammonium salts as recoverable phase-transfer catalysts for the asymmetric synthesis of alpha-amino acids.
Alkaloids such as cinchonidine, quinine and N-methylephedrine have been N-alkylated using polymeric benzyl halides or co-polymerized and then N-alkylated, thus affording a series of polymer-supported chiral ammonium salts which have been employed as phase-transfer catalysts in the asymmetric benzylation of an N-(diphenylmethylene)glycine ester. These new polymeric catalysts can be easily recove...
متن کاملOrganocatalytic enantioselective allylic alkylation of MBH carbonates with β-keto esters.
The highly stereoselective allylic alkylation of Morita-Baylis-Hillman carbonates with β-ketoesters catalysed by β-ICD is described. The corresponding products containing two adjacent quaternary and tertiary carbon centers were obtained in good yields with high diastereoselectivity (up to 10 : 1 dr) and enantioselectivity (up to 95% ee).
متن کاملEnantioselective alkylation of β-keto phosphonates by direct use of diaryl methanols as electrophiles.
Enantioselective alkylation of β-keto phosphonates with diaryl methanols in the presence of catalytic amounts of copper(II) trifluoromethanesulfonate and an optically active ligand gives the corresponding alkylated products in good to high yields with a high enantioselectivity.
متن کاملHighly Enantioselective Hydrogenation of a-Keto Esters Catalyzed by Ru-Tunephos Complexes Highly Enantioselective Hydrogenation of a-Keto Esters
SYNLETT 2006, No. 8, pp 1169–117215.05.2006 Advanced online publication: 10.03.2006 DOI: 10.1055/s-2006-932461; Art ID: W30605ST © Georg Thieme Verlag Stuttgart · New York Abstract: Various enantiomerically pure a-hydroxy esters were synthesized by asymmetric hydrogenation of a-keto esters catalyzed by Ru-Cn-Tunephos complex. Up to 97.1% ee has been achieved for both a-aryl and a-alkyl substitu...
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ژورنال
عنوان ژورنال: Arkivoc
سال: 2011
ISSN: 1551-7012
DOI: 10.3998/ark.5550190.0012.710