Alkylations heteropoly acids

In addition to CuCfi, some other compounds such as Cu(OAc)2, Cu(N03)2-FeCl.i, dichromate, HNO3, potassium peroxodisulfate, and Mn02 are used as oxidants of Pd(0). Also heteropoly acid salts comtaining P, Mo, V, Si, and Ge are used with PdS04 as the redox system[2]. Organic oxidants such as benzo-quinone (BQ), hydrogen peroxide and some organic peroxides are used for oxidation. Alkyl nitrites are unique oxidants which are used in some industrial... 

Heteropoly acids can be synergistically combined with phase-transfer catalysis in the so-called Ishii-Venturello chemistry for oxidation reactions such as oxidation of alcohols, allyl alcohols, alkenes, alkynes, P-unsaturated acids, vic-diols, phenol, and amines with hydrogen peroxide (Mizuno et al., 1994). Recent examples include the epoxidations of alkyl undecylenates (Yadav and Satoskar, 1997) and. styrene (Yadav and Pujari, 2000). 

Clay-supported heteropoly acids such as H3PW12O40 are more active and selective heterogeneous catalysts for the synthesis of MTBE from methanol and tert-butanol, etherification of phenethyl alcohols with alkanols, and alkylation of hydroquinone with MTBE and tert-butanoi (Yadav and Kirthivasan, 1995 Yadav and Bokade, 1996 Yadav and Doshi, 2000), and synthesis of bisphenol-A (Yadav and Kirthivasan, 1997). 

Cesium salts of 12-tungstophosphoric acid have been compared to the pure acid and to a sulfated zirconia sample for isobutane/1-butene alkylation at room temperature. The salt was found to be much more active than either the acid or sulfated zirconia (201). Heteropolyacids have also been supported on sulfated zirconia catalysts. The combination was found to be superior to heteropolyacid supported on pure zirconia and on zirconia and other supports that had been treated with a variety of mineral acids (202). Solutions of heteropolyacids (containing phosphorus or silicon) in acetic acid were tested as alkylation catalysts at 323 K by Zhao et al. (203). The system was sensitive to the heteropoly acid/acetic acid ratio and the amount of crystalline water. As observed in the alkylation with conventional liquid acids, a polymer was formed, which enhanced the catalytic activity. 

Davassy, B., Shanbhag, G., Lefebvre, F., and Halligudi, S. (2004) Alkylation of p-cresol with tert-butanol catalyzed by heteropoly acid supported on zirconia catalyst. J. Mol. Catal. A Chem., 210, 125-130. 

Studies with sulfated zirconia also show similar fast catalyst deactivation in the alkylation of isobutane with butenes. It was found, however, that original activities were easily restored by thermal treatment under air without the loss of selectivity to trimethylpentanes. Promoting metals such as Fe, Mn, and Pt did not have a marked effect on the reaction.362,363 Heteropoly acids supported on various oxides have the same characteristics as sulfated zirconia.364 Wells-Dawson heteropoly acids supported on silica show high selectivity for the formation of trimethylpentanes and can be regenerated with 03 at low temperature (125°C).365... 

When H3PM012O40 was used to catalyze acylation reactions some of the acid dissolved and the reactions were partially promoted by the acid in solution. The H4SiW]204o and H3PW12O40 catalysts, however, did not dissolve under the reaction conditions and were, therefore, effective promoters for liquid phase Freidel-Crafts acylation reactions.Supported and bulk heteropoly acids have also been used to promote vapor phase Freidel-Crafts alkylations and esterifications.. ... 

Vapor-phase alkylation of phenol with ferf-butyl alcohol in the presence of trivalent iron-substituted molecular sieve catalysts (FeMCM-41) gives para-fert-butylphenol with high regioselectivity . Supported heteropoly acid catalysts have been used in the heterogeneous alkylation reactions of 1-octene or nonene with phenol at 80-100°C. The catalyst H4SiWi204o/Si02 gives 90% para-alkylphenol and 10% orf/zo-alkylphenol. 

Nitroethene is sufficiently electrophilic to substitute indole without the need for acid catalysis. Despite this, it has been shown that siUca-gel-supported CeCl3.7H20/NaI brings about such reactions at room temperature under solvent-free conditions or, to take another solvent extreme, the reaction occurs in water with a catalytic amount of a heteropoly acid (H3PWi204o). The employment of 2-dimethylamino-l-nitroethene in trifluoroacetic acid leads to 2-(indol-3-yl)nitroethene - the reactive species is the protonated enamine and the process is similar to a Mannich condensation (20.1.1.9). The use of 3-trimethylsilyl-indoles, with tpxo-substitution of the silicon, is an alternative means for effecting alkylation, avoiding the need for acid catalysis. 

Several zeolites in the II-form, two activated clays, a silica-alumina, a sulfonic acid resin and a silica-occluded heteropoly acid were tested in the reaction of cyclohcxcne and toluene (excess) at 110 °C [64]. The ortho / meta / para ratio of the mixtures strongly depends on the structure of the catalysts involved. With zeolite H-USY and Filtrol-24 as active catalysts the meta / para ratio is found to be about 2 1, in agreement with the thermodynamic equilibrium, and the ortho-isomer is essentially absent.By contrast 11-Bcta and H-mordenite gave a meta /para ratio of 1 4.5. As H-USY appeared to be a good isomerization catalyst for the cyclohexyltoluenes, the mechanism may involve ortho / para-alkylation followed by isomerization. Researchers of UOP (Dcs Plaines, USA) found a separation method for meta / para cyclohexyltoluenc (undisclosed technique). Altogether the results open a new low-waste route to 3-methylbiphenyl. 

Cs" salts catalyse the acylation of toluene, p-xylene and m-xylene with crotonic acid. Some alkylation of aromatic compounds with crotonic acid also takes place. Heteropoly acid was found to be more active than zeolites HY and H-Beta in the acylation. 

P-16 - Alkylation of isopropylnaphthalene over heteropoly acid catalysts supported on mesoporous materials... 

Grafting, one-step or two-step 29-P-3I Heteropoly acid, alkylation catalyst 25-P-16... 

The Friedel-Crafts alkylation of indoles could also be performed in water, as presented in Figure 21, with yields as high as 97% in the presence of Keggin heteropoly acids, solid superacid catalysts [40]. 

Mizuno N, Misono M (1998) Heterogeneous eatalysis. Chem Rev 98 199-218 Briand LE, Baronelti LE, Thomas HJ (2003) The state ofthe artonWells-Dawson heteropoly-compounds a review of their properties and applications. J Mol Catal A Gen 256 37-50 Hemender K, Reddy A, Pandurange Reddy V, Veeragaiah V (1992) Versatile synthesis of 6-alkyl/aryl-l/7-pyrazolo[3,4-d]pyrimidin-4[5//]-ones. Ind J Chem 316 163 166 Misono M, Okuhara T (1993) Solid superacid catalysts. Chem Tech 23(1I) 23 29 Kozhevnikov IV (1987) Advances in catalysis by heteropolyacids. Russ Chem Rev 56 811-825 Izumi Y, Urabe K, Onaka M (1992) Zeolite, elay and heteropoly acid in organic reaction, vol 99. Kodansha, Tokyo... 

Firouzabadi and coworkers reported aluminum dodecatungstophosphate (AIPW12 O40) as a water tolerant, highly active, and reusable catalyst for the preparation of benzylic alkyl or symmetrical dibenzylic ethers from their corresponding alcohols (Scheme 6.7) [7a]. This heteropoly acid catalyst was also applied to the preparation of diphenylmethylsulfides from diphenylmethanol and a variety of thiols [7bj. 

Various kinds of oxide materials, including single oxides, mixed oxides, molybdates, heteropoly-ions, clays, and zeolites, are used in catalysis they can be amorphous or crystalline, acid or basic. Furthermore the oxides can be the actual catalysts or they can act as supports on which the active catalysts have been deposited. Silica and alumina are commonly used to support both metals and other metal oxide species. Amorphous silica/alumina is a solid acid catalyst, it is also used as a support for metals, when bifunctional (acid and metal) catalysis is required, e.g., in the cracking of hydrocarbons. Other acid catalysts are those obtained by the deposition of a soluble acid on an inert support, such as phosphoric acid on silica (SPA, used in the alkylation of benzene to cumene. Section 5.2.3). They show similar properties to those of the soluble parent acids, while allowing easier handling and fixed bed operation in commercial units. 

Typic2il examples of acid-catalysis of heteropoly compounds are as follows Dehydration of methanol, - > ethanol, - - propanol - - - -"- "- > and butanol, conversion of metanol or dimethyl ether to hydrocarbons, etheration to form methyl /-butyl ether, esterifications of acetic acid by ethanol and pentanol, decomposition of carboxylic acid and formic acid, alkylation of benzene by ethylene and isomerization of butene, o-xylene and hexane. ... 

---