Carboxylic acids catalyst immobilization

Aldehydes may be converted to carboxylic acids using Ni(acac)2 immobilized in [bmim][PF,5], with oxygen as the oxidant, as shown in Scheme 9.14 [27], A similar reaction has also been performed using perfluorinated solvents, and it was found that there was little difference between the two systems [28], However, the Ni(acac)2 catalyst could not be used directly in the fluorous solvent and therefore the 1,3-diketonate was modified with long perfluorinated chains prior to use to ensure solubility. 

Bahrami K, Khodaei MM, Farrokhi A (2009) Highly efficient solvent-free synthesis of dihydropyrimidinones catalyzed by zinc oxide. Synth Commun 39 1801-1808 74. Gross GA, Wurziger H, Schober A (2006) Solid-phase synthesis of 4,6-diaryl-3,4-dihydro-pyrimidine-2(lH)-one-5-carboxylic acid amide derivatives a Biginelli three-component-condensation protocol based on immobilized beta-ketoamides. J Comb Chem 8 153-155 Desai B, Dallinger D, Kappe CO (2006) Microwave-assisted solution phase synthesis of dihydropyrimidine C5 amides and esters. Tetrahedron 62 4651 664 Kumar A, Maurya RA (2007) An efficient bakers yeast catalyzed synthesis of 3,4-dihydro-pyrimidin-2-(lH)-ones. Tetrahedron Lett 48 4569-4571 77. Zalavadiya P, Tala S, Akbari J, Joshi H (2009) Multi-component synthesis of dihydropyrimidines by iodine catalyst at ambient temperature and in-vitro anti mycobacterial activity. Arch Pharm 342 469-475... 

They immobilized azabicyclo[3.3.0]octane-3-carboxylic acid 7 both by grafting and by polymerization (Fig. 4). The addition of diethyl zinc to ben-zaldehyde in a column was studied. It was found that the monoUthic catalyst prepared by polymerization turned out to be superior (up to 99% ee) compared to the catalyst prepared by grafting (compare with Schemes 7 and 8). Differences in appropriate chiral cavities inside the polymer may be responsible for these results, the other factors being differences in reaction conditions and most probably the avoidance of diffusional problems in the monoUthic catalyst at high flow rates. 

Hydrogen peroxide can react with carboxylic acid to form peracid when lipase enzyme is used as a catalyst instead of inorganic acid. The peracid will epoxidize alkenes, which results in the regeneration of the carboxylic acid (Scheme 7). The best results were obtained in the nonpolar solvents toluene and hexane or when mixtures of alkene and carboxylic acid were used without solvent (55). Lipases were immobilized on cellulose, polysulfone membranes, or polypropylene beads (56). The lipases were used to convert caprylic acid to its peracid. The peracid was used to convert oleic acid to its epoxide. The best yield of epoxy stearic acid (81%) was obtained with the lipase from Candida antartica. Using a commercial preparation of immobilized C. antartica lipase, various unsaturated carboxylic acids were treated with... 

Chakraborti, A.K., Singh, B., Chankeshwara, S.V., Patel, A.R. 2009. Protic acid immobilized on solid support as an extremely efficient recyclable catalyst system for a direct and atom economical esterification of carboxylic acids with alcohols. Journal of Organic Chemistry 74 5967-5974. 

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