共查询到20条相似文献,搜索用时 15 毫秒
1.
I. V. Kozhevnikov A. I. Tsyganok M. N. Timofeeva S. M. Kulikov V. N. Sidelnikov 《Reaction Kinetics and Catalysis Letters》1992,46(1):17-23
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, - - . 相似文献
2.
I. V. Kozhevnikov I. B. Vasilieva V. V. Zarutskii 《Reaction Kinetics and Catalysis Letters》1992,47(1):83-86
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.
L-— L- — -L- 85% 0.1–0.35% H3PW12O40 H4SiW12O40 .相似文献
3.
Alkylation of p-cresol with tert-butanol catalyzed by heteropoly acid supported on zirconia catalyst
Biju M. Devassy G. V. Shanbhag F. Lefebvre S. B. Halligudi 《Journal of molecular catalysis. A, Chemical》2004,210(1-2):125-130
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%. 相似文献
4.
[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. 相似文献
5.
A. V. Arkhipova K. V. Malkova T. N. Sokolova V. R. Kartashov 《Russian Journal of Applied Chemistry》2007,80(1):162-163
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. 相似文献
6.
V. E. Tarabanko V. N. Sidelnikov I. V. Kozhevnikov 《Reaction Kinetics and Catalysis Letters》1982,21(1-2):109-114
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.
, 18O2 CH3C16O2H–H2 16O 369 18O 44–54%, .相似文献
7.
Highly efficient ring opening reactions of epoxides with deactivated aromatic amines catalyzed by heteropoly acids in water 总被引:1,自引:0,他引:1
Najmedin Azizi 《Tetrahedron》2007,63(4):888-891
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. 相似文献
8.
I. V. Kozhevnikov S. M. Kulikov N. G. Chukaeva A. T. Kirsanov A. B. Letunova V. I. Blinova 《Reaction Kinetics and Catalysis Letters》1992,47(1):59-64
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.
, H3PW12O40 H4SiW12O40 2,3,5- 1--4--2- E K1, .相似文献
9.
10.
M. Khoobi A. Ramazani A. R. Foroumadi H. Hamadi Z. Hojjati A. Shafiee 《Journal of the Iranian Chemical Society》2011,8(4):1036-1042
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. 相似文献
11.
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. 相似文献
12.
5-磺基水杨酸催化两相法合成某些二茂衍生物 总被引:2,自引:0,他引:2
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。 相似文献
13.
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%. 相似文献
14.
I. V. Kozhevnikov A. Sinnema A. J. A. van der Weerdt H. van Bekkum 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):63-70
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. 相似文献
15.
水溶性Rh-BISBIS配合物对阿维菌素催化加氢的研究 总被引:1,自引:0,他引:1
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. 相似文献
16.
Study of silica-supported heteropoly acids by microcalorimetry 总被引:1,自引:0,他引:1
Frédéric Lefebvre Bernadette Jouguet Aline Auroux 《Reaction Kinetics and Catalysis Letters》1994,53(2):297-302
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. 相似文献
17.
<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. 相似文献
18.
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. 相似文献
19.
S. N. Makhno N. V. Konoshchuk T. V. Chernyavska A. G. Dyachenko 《Russian Journal of Applied Chemistry》2013,86(12):1880-1884
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. 相似文献