Catalyst reusable solid

Mannich reaction. Reaction between ketene silyl acetals and aldimines occurs in the presence of sulfated zirconia in MeCN at room temperature. The reusable solid catalyst is easily recovered. 

Cycloaddition of CO and Epoxides over Reusable Solid Catalysts... 

Keywords. Cycloaddition, COj, cyclic organic carbonates, epoxides, reusable solid catalysts... 

Rapolu, R.K., NabaMukul, B.M., Bommineni, S.R., Potham, R., Mulakayala, N., Oruganti, S. 2013. Silica sulfuric acid A reusable solid catalyst for the synthesis of N-substituted amides via the Ritter reaction. RCS Advances 3 5332-5337. 

Desai, U.V., Thopate, T.S., Pore, D.M. and Wadgaonkar, P.P. 2006. An efficient, solvent-free method for the chemoselective synthesis of acylals from aldehydes and their deprotection catalyzed by silica sulfuric acid as a reusable solid acid catalyst. Catal. Commun. 7(7) 508-511. 

Santiago-Portillo A, Navalon S, Cirujano EG, Llabres i Xamena EX, Alvaro M, Garcia H. MIL-101 as reusable solid catalyst for autoxidation of benzylic 2 hydrocarbons in the absence of additional oxidizing reagent. ACS Catal 2015 5 3216-24. 

It was shown (Overberger and Sannes, 1974) that the polymeric imidazole was about 10 times as reactive as the monomeric imidazole in the hydrolysis of p-nitrophenyl acetate and certain 3-nitro-4-acyloxybenzoic acids. The increased catalytic activity of the polymeric imidazoles has been attributed to the cooperative interactions of the imidazole moieties anchored on the polymer chain at regular intervals (Scheme 13-3). Although practical applications of polyvinylimidazoles as catalytic nucleophiles in ester hydrolysis have not been made, it appears that they can provide quite effective and reusable solid-phase catalysts for such reactions. 

Catalyst Per-6-amino-p-cyclodextrin (per-6-ABCD) — acts as a supramolecular host and a reusable solid base catalyst... 

Khaligh, N. G. Ultrasound-assisted one-pot synthesis of substituted coumarins catalyzed by poly(4-vinylpyridinium) hydrogen sulfate as an efficient and reusable solid acid catalyst. Ultrason. Sonochem. 2013, 20,1062-1068. 

The resulting solids were used as enantioselective catalysts in cyclopropa-nation, Diels-Alder and ene reations. In many cases, the recoverability and reusability of these catalysts were carefully studied and this aspect has been the driving force for new research. 

The oxidation of methyl phenyl sulfide using fresh PWAA gave methyl phenyl sulfone in 97% yield. In the repeated use of recovered catalyst, the yields of sulfone in runs 2 to 5 ranged from 82 to 88%. The activities of recovered catalysts were somewhat reduced. The deactivation may be caused by catalyst pulverization or degradation of the PW12O403- species. While the reusability and stability of the catalyst should be improved, this concept would be useful for the creation of sophisticated solid catalysts. After Ikegami s reports, Neumann and coworkers [140] applied this strategy to the development of alkylated polyethyleneimine/POM synzymes. 

Perhaps, a more important reason for the little research in this particular area is the slow reaction rate associated with acid catalysis in general. However, the ability of solid acids to catalyze both esterification and transesterification reactions simultaneously and the possibility for employing catalysts that are reusable and green, meaning that they do not pose a great environmental threat, are attractive aspects that make the study of these materials imperative. 

Material 1 was also treated with 3-bromopropyltrichlorosilane to yield a propyl tether with a bromo-head group (4). Substitution with either trimethylamine or triethylamine to form the corresponding quaternary ammonium species, followed by ion exchange with potassium perruthenate afforded the catalytic species (5) and (6) respectively. The black solid 5 was found to be an equally efficient catalyst for the oxidation reactions and 6 was found to be a more highly active recoverable and reusable... 

A difficult problem in utilizing enzymes as catalysts for reactions in a non-cellular environment is their instability. Most enzymes readily denature and become inactive on heating, exposure to air, or in organic solvents. An expensive catalyst that can be used only for one batch is not likely to be economical in an industrial process. Ideally, a catalyst, be it an enzyme or other, should be easily separable from the reaction mixtures and indefinitely reusable. A promising approach to the separation problem is to use the technique of enzyme immobilization. This means that the enzyme is modified by making it insoluble in the reaction medium. If the enzyme is insoluble and still able to manifest its catalytic activity, it can be separated from the reaction medium with minimum loss and reused. Immobilization can be achieved by linking the enzyme covalently to a polymer matrix in the same general manner as is used in solid-phase peptide synthesis (Section 25-7D). 

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