Search results for "phase-transfer catalysi"

showing 3 items of 3 documents

Low-loading asymmetric organocatalysis

2011

Asymmetric organocatalysis is now recognized as the third pillar of asymmetric synthesis. Recent years have witnessed increasing interest towards the use of highly active and stereoselective organocatalysts. This critical review documents the advances in the development of chiral organocatalysts which are systematically used in ≤3 mol% loading in all the sub-areas of the field, namely aminocatalysis, Brønsted acids and bases, Lewis acids and bases, hydrogen bond-mediated catalysis, phase transfer and N-heterocyclic carbene catalyses (194 references).

AminocatalysisMolecular StructureOrganic chemicalsBronsted BaseEnantioselective synthesisPillarSettore CHIM/06 - Chimica OrganicaGeneral ChemistryCatalysisBronsted acidCatalysisoragnocatalysichemistry.chemical_compoundchemistryphase-transfer catalysiOrganocatalysisOrganic chemistryLewis acids and basesOrganic ChemicalsBrønsted–Lowry acid–base theoryCarbeneChem. Soc. Rev.
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O-Alkylation of a lignite humic acid by phase-transfer catalysis

2006

A mild phase-transfer catalytic reaction has been conducted to O-alkylate the acidic functions of a lignite humic acid (HA), using tetrabutylammonium hydroxide as the phase-transfer catalyst. The HA acidic functional groups were made to react, in tetrahydrofuran, by nucleophilic substitution with several alkyl halides-methyl iodide, and ethyl, propyl, and butyl, and benzyl bromide. The occurrence of the O-alkylation reaction was assessed by elemental analysis and 1H NMR, CPMAS 13C NMR, and FTIR spectroscopy. Bonding of alkyl groups increased the carbon and hydrogen content and the H/C ratios of all the humic reaction products. Increased nitrogen in the reaction products suggested incomplete…

chemistry.chemical_classificationSettore AGR/13 - Chimica AgrariaEtherAlkylationCarbon-13 NMRBiochemistryAnalytical ChemistryCatalysischemistry.chemical_compoundchemistryProton NMRNucleophilic substitutionHumic acidOrganic chemistrylipids (amino acids peptides and proteins)Humic substances O-Alkylation Phase-transfer catalysis Tetrabutylammonium hydroxide NMR FTIRAlkylAnalytical and Bioanalytical Chemistry
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Proximity Effect using a Nanocage Structure: Polyhedral Oligomeric Silsesquioxane-Imidazolium Tetrachloro- palladate Salt as a Precatalyst for the Su…

2016

A polyhedral oligomeric silsesquioxane-imidazolium tetrachloropalladate salt (POSS-Imi-PdCl4) was prepared by the reaction of a polyhedral oligomeric silsesquioxane-imidazolium chloride salt (POSS-Imi-Cl) with PdCl2 and used as a pre-catalyst for the Suzuki-Miyaura reaction in water at 100 °C at a low loading (0.08-0.16 mol %). Biphenyl compounds were isolated in high to excellent yields. A comparison of the POSS-based catalyst with the corresponding catalyst without the nanocage structure (i.e., 1-butyl-3-methylimidazolium tetrachloropalladate) highlighted the role of the POSS structure to reach higher yields in the Suzuki-Miyaura reaction. This result is ascribed to a proximity effect of …

chemistry.chemical_elementSalt (chemistry)supported catalyst010402 general chemistry01 natural sciencesCatalysisCatalysisInorganic Chemistrychemistry.chemical_compoundNanocagesX-ray photoelectron spectroscopyPolymer chemistryOrganic chemistrysupported catalystsPhysical and Theoretical Chemistrychemistry.chemical_classification010405 organic chemistryChemistryOrganic Chemistrypalladiumcage compoundSilsesquioxane0104 chemical sciencesBiphenyl compoundphase-transfer catalysiphase-transfer catalysisC-C couplingcage compoundsProximity effect (atomic physics)Palladium
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