Alkylation of p-substituted phenols by heteropoly acids

Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H₃PW₁₂O₄₀ and 25% H₃PW₁₂O₄₀/SiO₂ at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H₂SO₄, easily separated from the reaction mixture and can be used repeatedly. -- () - () H₃PW₁₂O₄₀ 25% H₃PW₁₂O₄₀/SiO₂ 100–150°C - - . , H₂SO₄, - - .     

Acetonation of L-sorbose catalyzed by heteropoly acids

Acetonation of L-sorbose—a step of ascorbic acid synthesis—takes place in acetone to yield 85% of diacetone-L-sorbose in the presence of heteropoly acids H₃PW₁₂O₄₀ and H₄SiW₁₂O₄₀ (0.1–0.35%) as catalysts.

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L-— L- — -L- 85% 0.1–0.35% H₃PW₁₂O₄₀ H₄SiW₁₂O₄₀ .

     

Alkylation of p-cresol with tert-butanol catalyzed by heteropoly acid supported on zirconia catalyst

Butylation of p-cresol by tert-butanol was catalyzed by 12-tungstophosphoric acid supported on zirconia (TPA/ZrO₂) under flow conditions. Catalysts prepared with different TPA loading (5–30 wt.%) were calcined at 1023 K and acidity was estimated by temperature programmed desorption (TPD) of NH₃. Fifteen percent TPA/ZrO₂ showed the highest acidity and found to be the most active catalyst in butylation of p-cresol. The effects of temperature, space velocity (LHSV) and molar ratio of the reactants on the conversion of p-cresol and products selectivities were optimized and the optimum reaction conditions evaluated were 403 K, tert-butanol/p-cresol (Bu/Cr) molar ratio 3 and LHSV 4 h⁻¹. Under the optimized conditions, conversion of p-cresol was found to be 61 mol% with product selectivity for 2-tert-butyl-p-cresol (TBC) 81.4%, 2,6-di-tert-butyl-p-cresol (DTBC) 18.1% and tert-butyl-p-tolyl ether (ether) 0.5%. Study of time on stream (TOS) performed as a function of time for 100 h showed that the loss in activity in terms of conversion of p-cresol was 6%.     

Highly efficient one-pot three-component Mannich reaction in water catalyzed by heteropoly acids

[reaction: see text] Heteropoly acids efficiently catalyzed the one-pot, three-component Mannich reaction of ketones with aromatic aldehydes and different amines in water at ambient temperature and afforded the corresponding beta-amino carbonyl compounds in good to excellent yields and with moderate diastereoselectivity. This method provides a novel and improved modification of the three-component Mannich reaction in terms of mild reaction conditions and clean reaction profiles, using very a small quantity of catalyst and a simple workup procedure.     

Synthesis of a new thiocarbamate by the reaction of benzyl thiocyanate with camphene,catalyzed by heteropoly acids

The reaction of benzyl thiocyanate with camphene in the presence of heteropoly acids, 12-phosphotungstic and 12-silicotungstic, at 65 C was studied. S-Benzyl (1,7,7-trimethylnorbornyl)thiocarbamate was prepared in 66% yield.     

Mechanism of the liquid-phase oxidation of diethyl sulfide catalyzed by heteropoly acids

It has been established that in the oxidation of diethyl sulfide by¹⁸O₂ in CH₃C¹⁶O₂H–H₂ ¹⁶O solution at 369 K catalyzed by heteropoly acids, sulfoxide and sulfone with 44–54%¹⁸O enrichment are formed. The process is accompanied by isotope exchange of molecular oxygen.

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, ¹⁸O₂ CH₃C¹⁶O₂H–H₂ ¹⁶O 369 ¹⁸O 44–54%, .

     

Highly efficient ring opening reactions of epoxides with deactivated aromatic amines catalyzed by heteropoly acids in water

Heteropoly acid was found to be an effective and efficient catalyst for the ring opening reaction of epoxides with various aromatic amines to produce the corresponding β-amino alcohols in moderate to excellent yields in water. This method provides a new and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst, and simple work-up procedure.     

Syntheses of vitamins E and K1 catalyzed by heteropoly acids

Heteropoly acids H₃PW₁₂O₄₀ and H₄SiW₁₂O₄₀ have been found to be efficient catalysts for condensation of isophytol with 2, 3, 5-trimethylhydroquinone and 1-acetoxy-4-hydroxy-2-methyl-naphthalene in the syntheses of vitamins E and K₁, respectively.

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, H₃PW₁₂O₄₀ H₄SiW₁₂O₄₀ 2,3,5- 1--4--2- E K₁, .

     

Efficient microwave-assisted synthesis of 3-benzothiazolo and 3-benzothiazolino coumarin derivatives catalyzed by heteropoly acids

Heteropoly acids are reported as efficient catalysts for the microwave-assisted synthesis of 3-benzothiazolo and 3-benzothiazolino coumarin from o-aminothiophenol derivatives with 3-acetly and 3-cyanochromen-2-one in good to excellent isolated yields (73?C95%). This study suggests new techniques for the synthesis of chromene derivatives using an inexpensive and easily available catalyst, a simple procedure, short reaction time, and good to excellent yields of the products.     

Aza-Michael addition reactions between nitroolefins and benzotriazole catalyzed by MCM-41 immobilized heteropoly acids in water

MCM-41 supported heteropoly acids(HPAs) catalysts were synthesized,characterized and their catalytic activity was evaluated in an aza-Michael addition reaction between nitroolefins and benzotriazole in water at room temperature.50 wt% PW/MCM-41 showed the highest activity(up to 96% yield).The catalyst was used in six consecutive experiments without obvious loss of activity, confirming the success of the anchoring process and the catalyst stability.     

5－磺基水杨酸催化两相法合成某些二茂衍生物

首次利用5－磺基水杨酸作为催化剂合成了9种二茂钛衍生物,经元素分析,UV－vis,IR及^1HNMR等对配合物结构进行了表征,并利用电子吸收光谱对取代水杨酸参与反应的机理进行了探讨,同时发现,5－磺基水杨酸水溶液也可用于二氯二茂钛的分离,并且非常有效。     

Synthesis of spirobiindanes via bis-cyclization reaction of the 1,5-diaryl-3-pentanones catalyzed by heteropoly acids

Bis-cyclization reaction of the 1,5-diaryl-3-pentanones catalyzed by heteropoly acids (HPAs) was examined for the first time, and a series of spirobiindanes were synthesized. 1,5-Diaryl-3-pentanones were refluxed and dehydrated in toluene in the presence of 0.15 equiv of a heteropoly acid to furnish spirobiindanes in moderate to high yield. For the known 4,4′-dibromo-7,7′-dimethoxy-1,1′-spirobiindane, the yield was upgraded from 66% to 80%.     

Hydration and acetoxylation of dihydromyrcene catalyzed by heteropoly acid

The liquid-phase hydration and acetoxylation of the monoterpene dihydromyrcene (DHM, 3,7-dimethyl-1,6-octadiene) are efficiently catalyzed by Keggin-type heteropoly acid H₃PW₁₂O₄₀ (HPA) at 14–30°C to yield dihydromyrcenol (DHM---OH, 2,6-dimethyl-7-octen-2-ol) and dihydromyrcenyl acetate (DHM---OAc). Homogeneous, biphasic (DHM/AcOH-H₂O-HPA) and heterogeneous (with HPA/SiO₂ catalyst) reactions have been studied. HPA has a much higher catalytic activity than conventional acid catalysts such as H₂SO₄ and Amberlyst-15. A synthetically useful biphasic acetoxylation/hydration of DHM has been developed. The method provides a 90% selectivity to the sum of DHM---OH and DHM---OAc at 21% DHM conversion and allows for easy and clean catalyst recycling without loss of activity.     

水溶性Rh-BISBIS配合物对阿维菌素催化加氢的研究

The hydrogenation of avermectin catalyzed by [RhCl(COD)]_2-BISBIS[COD:1,5-cyclooctadiene,BISBIS:sulfonated 1,1'-bis(diphenylphosphino Methyl-2,2'-biphenyl)] in situ in aquenous/organic two-phase system was studied.The influence of various parameters,such as the surfactant concentration,the molar ratio of rhodium to phosphine,the reaction temperature and pressure on this hydrogenation were investigated.The results showed that the hydrogenation activities of diphosphine was higher that of monophosphine.     

Study of silica-supported heteropoly acids by microcalorimetry

Silica-supported heteropoly acids have been studied by microcalorimetry. The results are greatly dependent on both the activation temperature and the heteropoly acid, in agreement with the n-hexane cracking experiments. It is shown that very strong acid sites are formed on H₄SiW₁₂O₄₀/SiO₂ activated at 623 K and on H₃PW₁₂O₄₀/SiO₂ activated at 423 K.     

Highly efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by heteropoly acids in water

<正>Heteropoly acids efficiently catalyzed the cyclocondensation reaction of anthranilamide with aldehydes in water at ambient temperature and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields.This method provides mild reaction conditions and clean reaction profiles,using a small quantity of catalyst and a simple workup procedure.     

Luminol chemiluminescence under interaction with heteropoly acids

Interaction of luminol with phosphomolybdic, phosphovanadomolybdic and silicomolybdic acids was studied by examination of chemiluminescence spectra, measurement of ESR spectra, investigation of reaction order, and elucidation of inhibition effects. A scheme of the reaction mechanism is proposed.     

Electrophysical properties of polyaniline doped with heteropoly acids

Composites of polyaniline with phosphotungstic and phosphomolybdic heteropoly acids of Keggin type were studied by impedance spectroscopy. Doping of polyaniline with these acids allows the proton conductivity of the polymer in the composites to be increased by six orders of magnitude.