Search results for "phase-transfer catalysis"
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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…
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 …