pKa values of chiral Brønsted acid catalysts: phosphoric acids/amides, sulfonyl/sulfuryl imides, and perfluorinated TADDOLs (TEFDDOLs).
نویسندگان
چکیده
منابع مشابه
Palladium(II)/Brønsted Acid-Catalyzed Enantioselective Oxidative Carbocyclization–Borylation of Enallenes**
An enantioselective oxidative carbocyclization-borylation of enallenes that is catalyzed by palladium(II) and a Brønsted acid was developed. Biphenol-type chiral phosphoric acids were superior co-catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess.
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Enantioenriched secondary alcohols represent an important class of molecules found in numerous intermediates, chiral building blocks, and biologically active compounds. Asymmetric reduction of prochiral ketones constitutes the most straightforward way to form these important moieties. Traditionally, stoichiometric amounts of chiral ligands were used together with an aluminium or a boron hydride...
متن کاملEnantioselective Nazarov cyclization of indole enones cooperatively catalyzed by Lewis acids and chiral Brønsted acids† †Electronic supplementary information (ESI) available: For CIF data of (R)-3r, experimental procedures, spectral data, and computational study results. CCDC 1539722. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc03183a Click here for additional data file. Click here for additional data file. Click here for additional data file.
Enantioselective control of the chirality of a tertiary a-carbon in the products of a Nazarov cyclization of enones is challenging because the reaction involves an enantioselective proton transfer process. We herein report the use of cooperative catalysis using Lewis acids and chiral Brønsted acids to control the stereochemistry of the tertiary a-carbon in the products of this reaction. Specifi...
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A novel study of external Brønsted acid-assisted thiourea catalysts in the asymmetric FriedelCrafts alkylation of indoles with nitroalkenes is reported. The final 3-substituted indoles derivatives are synthesized with better results by cooperative effect between chiral thiourea and a Brønsted acid additive (1a·HA), than those obtained with sole thiourea catalyst 1a. The effect of diverse catal...
متن کاملWhen gold meets chiral Brønsted acid catalysts: extending the boundaries of enantioselective gold catalysis.
This review describes the development in the use of Au(I)/Brønsted acid binary catalytic systems to enable an enantioselective transformation in one-pot that cannot be achieved by gold catalysts alone. The examples discussed herein are promising since apart from using chiral ligands there exists a possibility of using chiral Brønsted acids. Clearly, the horizon for enantioselective gold catalys...
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ورودعنوان ژورنال:
- Chemistry
دوره 17 31 شماره
صفحات -
تاریخ انتشار 2011