Ion exchange resins Amberlyst

Scott Oakes et al. (1999a, b) have shown how adoption of SC conditions can lead to a dramatic pressure-dependent enhancement of diastereoselectivity. In the case of sulphoxidation of cysteine derivatives with rert-butyl hydroperoxide, with cationic ion-exchange resin Amberlyst-15 as a catalyst, 95% de was realized at 40 °C and with SC CO2. By contrast, with conventional solvents no distereoselectivity was observed. Another example is the Diels-Alder reaction of acrylates with cyclopentadiene in SC CO2 at 50 °C, with scandium tris (trifluoromethanesulphonate) as a Lewis acid catalyst. The endoiexo ratio of the product was as high as 24 1, while in a solvent like toluene it was only 10 1. 

Yuen et al. [24] first demonstrated the nature of the information that can be obtained regarding chemical mapping within a fixed-bed reactor, using the liquid phase esterification of methanol and acetic acid catalyzed within a fixed bed of H+ ion-exchange resin (Amberlyst 15, particle size 600-850-pm) catalyst as the model... 

Needing 2,5-dimethylfuran as a masked 1,4-dicarbonyl equivalent, Scott and Naples found that the ion-exchange resin Amberlyst 15 is extremely effective in catalyzing the cyclization of hexane-2,5-dione to this compound.31 Some unusual Paal-Knorr reactions have been described. In one, phos-phorus(V) sulfide gave none of the expected thiophene when it acted upon the diketoester 3, the thioester 4 being obtained instead.32 Against all... 

HNF2 reacts with saturated and unsaturated mono- and diacetals at ambient temperature to 100°C (250) and also smoothly in the presence of a sulfonic acid ion-exchange resin (Amberlyst-15) (140, 276) to give a-difluoroamino ethers (140). These compounds react with a second molecule of HNF2 in the presence of sulfuric acid to give bis(difluoro-amino) derivatives (140). 

These zirconium phosphate materials are being developed as replacements for ion exchange resin catalysts. The arylsulfonic acid MELS have been evaluated for butene isomerization, methanol dehydration, MTBE synthesis as well as cracking, and for the alkylation of aromatics. In the synthesis of MTBE this catalyst appears to out-perform the ion exchange resins, Amberlyst 15. 

The efficacy of different catalysts at 50°C is given in the Fig.l. Among the catalysts used, HP A (unsupported and supported on KIO) and ion exchange resins (Amberlyst-15 and lndion-130) showed very high activities followed by sulphated zirconia, Filtrol-24 and KIO. The aluminium pillaring with SWy2 showed a little activity. Catalysts based on the zeolites such as H-ZSM-5, Y and mordenite did not show any activity. It appears that the pore sizes of these catalysts pose considerable intraparticle resistance for the reactant 2-MON to access the catalytic sites. 

R)-Nitroester 164 is produced in high yield by displacement of the mesylate 156b with the nitrate form of the ion-exchange resin Amberlyst A-26 [61]. The resin is prepared by washing the chloride form with aqueous potassium nitrate solution. The enantiomeric excess of the... 

The second group consists of reagents supported by ion exchange resins. Amberlyst resins are often used to support anionic nucleophiles, oxidants or reducing agents. Many of these ion exchange resins are commercially available or easily prepared from the chloride form (Scheme... 

Ion-exchange polymers. The above described perbromlde reagent can be obtained somewhat more easily the treatment of a commercial Ion exchange resin (Amberlyst A-26, bromide form) with molecular bromine In CCI4 (65) according to the method of Bonglnl et al. (Equation 12). Aside from the bromlnatlon of olefins. 

Some other modifications of the Bischler indole synthesis have been developed. One such modification is that of Moody and coworkers, who employed rhodium to effect N-H insertion of an a-diazo-p-ketoester to an aniline (Scheme 5, equations 1 and 2) [58-60]. The so-formed arylamino P-ketoester 16 was smoothly converted to indole 17 with the ion-exchange resin Amberlyst 15 or in somewhat lower yield with boron trifluoride etherate [59]. These workers extended the method to the synthesis of A-unsubstituted indoles using the novel A-protecting groups, A-(2-ethoxycarbonylethyl)... 

Investigation on the kinetics of the esterification reaction in the presence of the ion-exchange resin Amberlyst 15.The Uniquac model is applied to evaluate the activities of the reacting species in the kinetic equation. 

Mazzotti et al. (1996) studied the esterification of acetic acid with ethanol on a highly cross-linked sulphonic ion exchange resin (Amberlyst-15) in a continuous simulated moving bed reactor. The resin acted as catalyst as well as a selective sorbent simultaneously. They have studied the multicomponent sorption equilibria and swelling of the resin, as well as esterification kinetics with appropriate models. The thermodynamic and kinetic descriptions of the system have been combined to develop a fully predictive mathematical model of the chromatographic reactor. 

Kawase (1966) used simulated moving-bed reactor for production of phenethyl acetate from acetic acid and phenethyl alcohol with ion exchange resin Amberlyst 15 as catalyst. They proved that flow rates and temperature were the most important factors to achieve almost 100% conversion. Lode et al. (2001) used a simulated moving-bed reactor for recovery of dilute acetic acid from wastewater, by esterification with methanol in presence of ion exchange resin catalyst. They found that the overall efficiency of acetic acid recovery was about 96 percent. 

The kinetics and equilibrium of autocatalyzed and ion exchange resin (Amberlyst-15) catalyzed esterification of acetic acid with methanol and hydrolysis of methyl acetate were studied by Popken et. al. (2000) in a temperature range of 303 - 343 K. The homogeneous reaction has been described with a simple power-law model. To compare pseudo-homogeneous and adsorption-based kinetic models for the heterogeneously catalyzed reaction, independent binary liquid phase adsorption experiments were used to estimate the adsorption equilibrium constants to keep the number of adjustable parameters the same for each model. 

The application of ozone is a new and convenient way for the preparation of cyanoacetylaldehyde (3-oxopropylonitrile) (1) and its stable dimethyl acetal (3,3-dimethoxypropylonitrile) (2) used as valuable intermediates for organic synthesis [72]. For this purpose the ozonolysis of (E)-l,4-dicyano-2-butene or 3-butylonitrile is carried out. Then the oxidates are treated by DMS yielding 1. Further, compound 1 can be used either directly in the next reactions or is transformed into 2. The 2 output amounts to from 67 to 71%. The acetal can be again hydrolyzed to 1 by treatment with ion-exchange resin Amberlyst-15 [72]. 

---