Amberlysts

A solution of trifluoroacetic acid in toluene was found to be advantageous for cydization of pyruvate hydrazoncs having nitro substituents[4]. p-Toluene-sulfonic acid or Amberlyst-15 in toluene has also been found to give excellent results in preparation of indole-2-carboxylale esters from pyruvate hydra-zoiies[5,6J. Acidic zeolite catalysts have been used with xylene as a solvent to convert phenylhydraziiies and ketones to indoles both in one-flask procedures and in a flow-through reactor[7]. 

Amberlite IRA-402 Amberlite IRA-458 Amberlite IR-1180M Amberlite XAD Amberlite XAD-2 Amberlyst... 

Amberlyst H-15 (SO3H ion-exchange resin), dihydropyran, hexane, 1-2 h, 95% yield. ... 

MeO)3CH, anhydrous MeOH, TsOH, reflux, 2 h. Diethyl ketals have been prepared under similar conditions (EtOH, TsOH, 0-23°, 15 min-6 h, 80-95% yield) in the presence of molecular sieves to shift the equilibrium by adsorbing water. Amberlyst-15 or graphite bisulfate and (EtO)3CH have been used to prepare diethyl ketals. 

Amberlyst-15, acetone, H2O, 20 h, Aldehyde acetals conjugated with... 

Propanediol, THF, Amberlyst-15, 5 min, 50-70% yield. This method is also effective for the preparation of 1,3-dioxolanes. 

Isobutylene, Amberlyst H-15, hexane. Methylene chloride can also be used as solvent, and in this case a primary alcohol was selectively converted to the /-amyl ether in the presence of a secondary alcohol. ... 

AC2O, Amberlyst 15, 77% yield. These conditions introduce an acetyl group on oxygen in preference to the normally more reactive primary amine. ... 

IPA, NaOH, AC2O, pH 7.8. Phenols are selectively esterified in the presence of other alcohols. These authors also showed that an alcohol could be acetylated in the presence of an amine using AC2O and Amberlyst 15 resin. 

Amberlyst-15, acetone, H2O, 20 Aldehyde acetals conjugated with electron-withdrawing groups tend to be slow to hydrolyze. The use of HCl/THF or PPTS/acetone in the following case was slow and caused considerable isomerization. A TBDMS group is stable under these conditions. ... 

From a methyl enol ether 1,2-dihydroxymethylbenzene, Amberlyst H, 85% yield. ... 

Both 2,5-dialkyl-3-furoates and 2,5-dialkyl-3-phosphonofurans can be produced using the Paal-Knorr reaction. Methyl 2,5-diisopropyl-3-furoate (62) is available upon treatment of dione 61 with sulfuric acid. Phosphonodiones 63 can be efficiently converted into 2-substituted-3-diethylphosphono-5-methylfurans 64 by exposure to Amberlyst in refluxing toluene. ... 

Further improvements to this method have been reported by Bagley. The requirement of harsh thermal conditions to facilitate the cyclodehydration can be minimized by simply adding acetic acid or Amberlyst 15. Alternatively, one could use Lewis acids such as ZnBr2 or Yb(OTf>3 in catalytic amounts. 

Some work has also been achieved with heterogeneous catalysis. These catalysts include Amberlyst-15, Nafion-H, montmorillonite KSF clay, ferrihydrite silica gel aerogels containing 11-13% iron, silica sulfuric acid, and zeolites. ... 

Propargylsilanes can also be employed in the Sakurai reaction. For example the enone 6, containing a propargylsilane side chain, undergoes an intramolecular Sakurai reaction, catalyzed by an acidic ion-exchange resin—e.g. Amberlyst-15—to give stereoselectively the bicyclic product 7 in good yield ... 

A more effecdve catalyst for the Hetuy reacdon is a polymer-supported base such as amberlyst A-31. Various fi-nitro alcohols can be obtained v/ith the help of amberlyst v/ith or without solvent fEq, 3,14, A recent report claims that amberlite IRA-430 COH-formi or DOWEX-1 COH-formi is more effecdve for the Henry reacdon than amberlyst A-31/ Poly-... 

The heterogeneous catalytic systems have some advantages over homogeneous re Chemical transformations under heterogeneous conditions can occur v/ith better efficiencies, higher purity of products, and easier work-up Balliniandcoworkers have found that commercial amberlyst A-27 is the best choice for the Michael addition of nittoalkanes v/ith fi-subsdnited alkene acceptors fEq 4111 The reacdon is also carried out by potassium carbonate in the presence of Aliquat 336 under idttasonic irradiadon fEq 4 112 ... 

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