| Friedel—Crafts reactions usually take place in the presence of homogeneous catalysts, such as H2SO4, AlCl3, ect. However, those homogeneous catalysts have some unfavorable properties such as decomposition, reactor corrosion problems, difficulties in the separation of the catalysts. Therefore, efforts have been devoted to developing new solid acid processes that are environmentally benign. It is significant to investigate solid acids used in Friedel-Crafts reaction.Heteropolyacids (HPAs) have recently attracted attention as catalysts used in Friedel-Crafts reaction. They have been widely applied in catalysis due to their oxidation, acceptable stability, and high acidity. The disadvantages of bulk HPA as catalysts are their relatively low stability and surface area (1-10 m2/g). To overcome these disadvantages the HPA are usually supported on a suitable carrier that not only increases the available surface area but also improves the catalytic performance.In the present paper, the reaction of P-dimethoxybenzene withγ-butyrolactone, 4-Methoxyphenol with Methyl t-butyl ether under heteropolyacids and supported heteropolyacids were investigated, and the catalysts were characterized by various spectral and physicochemical techniques. The effects of reaction conditions and reaction mechanisms catalyzed by solid acid were further discussed. In addition, we introduce solid acid used in the Asymmetric Synthesis of Friedel-Crafts reaction.The main contents and results are as follows:1. H3PW12O40 supported on neutral Al2O3 and SiO2 were prepared by impregnation method. Their physicochemical properties such as dispersion, specific surface area, and so on were characterized by X-ray diffraction (XRD), N2 adsorption BET, Fourier transform infrared spectrum (FT-IR) and Raman spectrum. The results show that:①H3PW12O40 supported on neutral Al2O3 and SiO2 still kept the Keggin structure and were thermally more stable than pure H3PW12O40.②When H3PW12O40 loading amount was between 30%-40wt%, H3PW12O40 crystalline structure in XRD spectra was observed, and v(W=Od), v(W-Ob-W) appeared in IR spectra. Thus, a high dispersion of solute on the support surface between 30%-40wt% loading amount was got. In Raman spectra, the characteristic peaks of H3PW12O40 were able to be found when the loading amount was below 30wt% supporting on Al2O3 and SiO2. This is a useful way to study the structure of Heteropolyacids highly dispersed on support.2. Heteropolyacids were effective catalysts for the reaction of p-dimethoxybenzene withγ-butyrolactone. After analysis, it is confirmed that the product is 8-Hydroxy-5-methoxy-3, 4-dihydro-2H-naphthalen-l-one, while the expected product 5,8-dimethoxy-3,4-dihydro-2H-naphthalen-l-one(HMT) is not found. The present reaction is a novel one-step synthesis process of HMT. This paper focused on discussion of the effect of reaction conditions on the Yield or Selectivity and the possible reaction mechanisms. The reaction under the microwave irradiation was studied. The main results are as follows:①The reaction conditions to synthesize HMT under H3PW12O40 are optimized as follows: catalysts amount being 0.2-0.3g, molar ratio of DMB to BL being 3, reaction temperature being 190℃and reaction time being 3h. Reaction still takes place with small amount of water added into the mixture of reactants, but almost stops with large amount of water added.②Similar activity and selectivity are obtained under microwave irradiation condition for this reaction. But, it can save much more time under microwave comparing with under autoclave reactor.③The main reaction mechanisms: Reaction of p-dimethoxybenzene withγ-butyrolactone undergoes the Fries rearrangement processes, that is, gamma-butyrolactone is firstly ring-opened to form O-acylation intermediates, then further Fries rearrangement and intramolecular alkylation happen to produce the target product of HMT. The demethylation of 1, 4-dimethoxbenzene is detected in the reaction.3. Reaction of 4-Methoxyphenol with Methyl t-butyl ether was studied, for investigating catalyzing performance about heterpolyacids on different alumina supports and various reaction conditions. The main results are as follows: ①2-tert-butyl-4-methoxyphenol and 2 , 5-di-tert-butyl-4-methoxyphenol were synthesized via 4-Methoxyphenol with Methyl t-butyl ether over solid acid. Little 3-tert-butyl-4-methoxyphenol, 2, 6-di-tert-butyl-4-methoxyphenol and demethylation product were found in this reaction.②The catalytic behavior of catalysts with three different supports catalysts, basic, acidic and neutral alumina were studied. H3PW12O40 supported onto acidic supports, 4-Methoxyphenol could be easily protonated and much demethylated product was detected. The selectivity of 2-TBHA and 2, 5-DTBHA was lower than neutral supporter under the same condition. It was also observed that, when H3PW12O40 is supporting on basic alumina, the conversion of MOP remarkably decreases and the product yield is also lower comparing to neutral alumina. Thus, in the present paper we adopted neutral alumina as the supports.③Alkylation of 4-Methoxyphenol with MTBE was carried out by varying different parameters such as temperature, molar ratio of MTBE to MOP, amount of the catalyst and reaction time to optimize the conditions for maximum conversion as well as selectivity to product, under H3PW12O40 supported onto neutral alumina catalyst. It showed that the conversion of MOP increased remarkably with the loading amount increasing; When the loading amount is 30% to 40%, reaction temperature is 180℃, reaction time is 3h, the dosage of the catalyst is 0.3g and molar ratio of MTBE to MOP is 3, main product is 2-TBHA; It is favorable to the formation of 2,5-DTBHA when the amount of H3PW12O40 supported on neutral alumina is increasing, dosage of the catalyst is larger, the temperature is higher and the time of the reaction is longer.④The catalytic reusability was measured. After using four times, the conversion of reactants and yield of product did not drop obviously, indicating that the catalytic activity almost did not reduce. Thus, H3PW12O40 supported onto neutral alumina is a solid with good reusability in this reaction.4. The reaction of 2-(4'-Methylbenzenesulfonic acyoxy)ethyl Propionate and aromatic compound under acid catalysts was investigated. The results show that, reaction of (m-,p-,o-)xylene and 1,3,5-trimethylbenzene with 2-(4'-Methylbenzenesulfonic acyoxy)ethyl Propionate could convert to 2-arylpropanoic ester over AlCl3 catalyst. However, little target product was synthesized under AlCl3-NaCl and AlCl3 supported catalysts. In addition, under high temperature, heteropolyacids and trifluoromethanesulfonic acid salt, reactant mainly cracked to form side product not the target product.
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