Anisole acylation acetic anhydride

Tables 14.1 and 14.2 show the dramatic improvement brought by the substitution of the old technology with AICI3 catalyst and acetylchloride as acylating agent in a batch reactor by the new technology with a HBEA zeolite catalyst, acetic anhydride as acylating agent in a fixed bed reactor (12). The fixed bed reactor process constitutes a major break-through in anisole acetylation.

Cs2.5 for the acylation. Anisole and /j-xylene are acylated with benzoic anhydride and acetic anhydride in the presence of Cs2.5 without the dissolution of this catalyst. Carboxylic acids are much less reactive as acylating agents than the corresponding anhydrides because of the liberation of water. But when the water is removed, the acylation proceeds smoothly 214). Although the reaction of benzene with acetic acid is attractive in prospect, there is no report of heteropoly compounds as catalysts for this reaction. 

Amorphous and mesostructured Zr02 solid catalysts impregnated with various amounts of triflic acid were tested in the acylation of biphenyl356,357 and toluene358 (with benzoyl chloride and para-toluyl chloride, respectively, nitrobenzene solvent, 170°C and 130°C). All catalysts exhibited lower activity when compared with neat triflic acid. The mesoporous catalysts, however, showed complete selectivity in the formation of para-benzoylbiphenyl. A triflic acid-silica catalyst, in turn, prepared using an aminopropyl-modified silica, showed good characteristics in the solvent-less acetylation of anisole and 2-methoxynaphthalene with acetic anhydride.359,360 The activity of 1,1,2,2-tetrafluoroethanesulfonic acid, either neat or embedded in silica, was found to be similar to that of triflic acid in the acetylation of anisole.196... 

In 2001, Holderich s group [37] presented 1-methyl-3-butylimidazolium chlor-oferrate (Fe-IL) in addition to Al-IL and Sn-IL as a catalyst for Friedel-Crafts acylations. In the acetylation of anisole with acetic anhydride, full conversion of the acylating agent was observed using Fe-IL. The immobilization of these catalysts, however, led to some serious problems such as catalyst leaching. 

The set of catalysts selected for the dehydration of 2-butanol was also tested for the Friedel-Crafts acylation of anisole [69, 70]. The catalytic test was performed in the liquid phase due to the high boiling points of the reactants and products of this reaction. Anisole was reacted with acetic anhydride at 120 °C in the absence of solvent. In principle, acylation can occur on both the ortho and para positions of anisole. The main product (>99%) over all catalysts in this study was para-methoxyacetophenone, indicating that the reaction predominantly takes place inside the zeolite micropores. The same trend in catalytic activity as in the 2-buta-nol dehydration reaction is observed the conversion of anisole into para-nicihoxy-acetophenone increases upon increasing Ge content of the catalyst (Fig. 9.17) [67]. The main cause of deactivation for this reaction is accumulation of the reaction products inside the micropores of the zeolite. The different behavior of Ge-ZSM-5, compared with ZSM-5, may therefore be due to improved diffusional properties of the former, as the presence of additional meso- and macropores allows for... 

Readion of anisole (1) with acetic anhydride was chosen as a model, and ytterbium trifluoromethanesulfonate (ytterbium triflate, Yb(OTf)3) was the first RE(OTf)3 representative used. Several reaction conditions were examined the results are summarized in Table 1. When acetic anhydride, acetonitrile, or nitromethane was used as a solvent (entries 4—10), the reaction mixture became homogeneous and the acylation reaction proceeded smoothly. Nitromethane gave the highest yield of4-methoxyaceto-phenone (2) (entries 7-10). On the other hand, in carbon disulfide, dichloroethane, or nitrobenzene (entries 1-3), the reaction mixture was heterogeneous and the yield of 2 was low. It was noted that the acylation proceeded quantitatively when a catalytic amount of Yb(OTf)3 was used (0.2equiv., entry 9). Even when 0.05 equiv. of the catalyst was employed, 2 was obtained in 79 % yield (entry 10). 

A mixture of Yb(OTf)3 (620 mg, 1 mmol), anisole (1, 540 pL, 5 mmol), and acetic anhydride (940 pL, 10 mmol) in nitromethane (5mL) was stirred at 50 °C for 4h. After dilution with water (10 mL), the mixture was extracted with dichlorometh-ane. The organic layers were combined and dried over NaS04. After filtration and evaporation of the solvents, the crude mixture was purified by column chromatography on silica gel to afford 4-methoxyacetophenone (2). The aqueous layer was concentrated in vacuo to give a crystalline residue, which was heated at 190 °C for 4h in vacuo to afford 576.6 mg (93 %) Yb(OTf)3 as colorless crystals. The recovered Yb(OTf)3 was reused in the next acylation reaction. All products of the acylation of aromatic compounds shown in this chapter are known compounds and are commercially available. 

Subsequently, Corma and coworkers [49] reported the acylation of anisole with phenacetyl chloride over H-Beta and H-Y. The FC acylation of electron-rich heteroaromatics, such as thiophene and fur an, with acetic anhydride over modified ZSM-5 catalysts (Fig. 2.17) in the gas phase [50] or liquid phase [51] was also reported. 

Because a carboxylic anhydride and BF3 constitute a mild Friedel-Crafts acylating system, it is not surprising that nucleophilic aromatic substrates such as toluene, mesi-tylene, and anisole have been acetoacetylated [61]. The expected 1,3-diketones are formed when a sufficient excess of acetic anhydride is present in the reaction mixtures. The process is illustrated with anisole in Eq. (33) [61]. 

The selective acylating action of a mixed anhydride of two carboxylic acids was first correctly diagnosed by B hal, who showed that, in the acylation of an alcohol by a mixed anhydride, there preponderates (in the product) the ester formed from the acid having the smaller number of carbon atoms. The formation, from a mixture of acetic anhydride and either mono-, di-, or tri-chloroacetic acid, of an acetylating agent sufficiently powerful to effect p-acetylation of anisole was later demonstrated by Unger. ... 

Catalytic acylation of electron-rich aromatics is achieved with a combination of InCls and silver perchlorate (Scheme 8.114) [157]. Acetic anhydride, acetyl chloride and isopropenyl acetate serve as satisfactory acyl donors. By using an InCl3-impreg-nated Si-MCM-41 catalyst at low concentration, acylation of aromatic compounds (benzene, toluene, p-xylene, mesitylene, anisole, naphthalene, methylnaphfhalene, and methoxynaphfhalene) by acyl chlorides (benzoyl chloride, phenylacetyl chloride, propionyl chloride, or butyryl chloride) can be accomplished rapidly (3 h) at 80 °C in high yield, even in the presence of moisture in the aromatic substrate or solvent (dichloroethane) (Scheme 8.115) [158], In(OTf) j is an efficient catalyst in the sulfonylation of both activated and deactivated aromatic compounds (Scheme 8.116) [159]. 

Table 14.1 Acylation of anisole with acetic anhydride over different heterogeneous catalysts.

For the acylation of anisole by acetic anhydride over HBFA and HY, the reasons for the deactivation accord with those already reported for the reaction with veratrole. Unfortunately, di- or triketones were not extractible and, also, deactivation of the... 

To start our investigations, we examined the conversion of 2,3-dimethyl-2-butene (1) into 3,3,4-trimethyl-4-penten-2-one (2) as a model reaction (eq. 1). The choice of acetic anhydride as the acetylating agent was made in the light of related studies on the acylation of aryl ethers. Our work in this field had shown that acetic anhydride was the most effective reagent for the Friedel-Crafts acylation of anisole in the presence of Hp zeolite. A lower degree of conversion was achieved with acetyl chloride, while hardly any reaction occurred with ethyl acetate or acetic acid [6]. 

Anisole can be acylated with acetic anhydride in 99% yield (6.12). Yttterbium triflate can also be used. The yields are low when there is no activating group in the ring. The rate is accelerated by the addition of lithium perchlorate.56 Acylation of alcohols works well with 1 mole% of scandium triflate as a catalyst (6.13).57 The less toxic toluene has also been used as the solvent in such acylations. The... 

The acetylation of alcohols and phenols with acetic anhydride and HSZ-360 zeolite at 60oC used no solvent. The acetate of 1-dodecanol was obtained in 98% yield, and the acetate from 1 naphthol in 100% yield.183 The acylation of anisole with acetic anhydride at 100oC without solvent using zeolite H-/8 gave 4-methoxyacetophenone (6.30) in 98%yield.184 The catalyst could be recovered, regenerated, and reused with no decrease in yield. These reactions show that not all zeolites are used at high temperatures in the vapor phase. 

In the acylation of anisole by acetic anhydride, bismuth trichloride appears as a better catalyst than iron and zinc chlorides (Table 4, entries 2,5,6). 

H. M. C. 2004. Friedel-Crafts acylation of anisole with acetic anhydride over silica-supported heteropolyphosphotungstic acid (HPW/SiOj). /. Mol. Catal. A Chem. 209 189-197. 

Bachiller-Baeza, B. and Anderson, J. A. 2004. FTIR and reaction studies of the acylation of anisole with acetic anhydride over supported HPA catalysts. /. Catal. 228 225-233. 

B. 2007. Continuous acylation of anisole by acetic anhydride in mesoporous solid acid catalysts reaction media effects on catalyst deactivation. ]. Catal. 245 184-190. 

Thus, the Rhodia company developed and applied an industrial process for fhe acylation of anisole with acetic anhydride over BEA zeolite to selectively give para-acetylanisole. Furthermore, the reaction of isobutyl-benzene with the same acylating agent leads with high yield and selectivity to para-acetyl isobutylbenzene, which is an intermediate in the synthesis of ibuprofen, an important anti-inflammatory drug. ... 

Acylation is the most important method for the synthesis of aryl ketones that, in turn, are used for the preparation of many fine chemicals. In order to test the performance of the prepared catalysts, previous to their use in 2-methoxynaphtalene acylation, anisole acylation with acetic anhydride in a batch reactor is carried out, using the immobilized aluminium or copper salts of tungstophosphoric and tungstosilicic acids as catalysts. 

More recently, Gaare and Akporiaye (1996) studied the acylation of anisole by acetyl chloride and acetic anhydride. They observed that the activity of La-exchanged H-Y zeolite depends on the lantanum content. In fact, as can be seen in fig. 11, the highest yield to acylated compounds was obtained on catalysts with a 93% exchange. However, the activity to acylation reactions depends not only on the catalyst compositions but also on the acylating agents. Thus, it has been shown that activities for the acylation of anisole increases in the order benzoyl < acetyl < propionyl chloride, but, in all cases, a high selectivity to the para isomer was observed (Akporiaye et al. 1993). 

Izumi et al. pioneered the use of heteropoly acids as catalysts for aromatic acylation. Silica-supported acids H4[SiWi204o] and H3[PWi204o] were found to effectively catalyse the acylation of p-xylene with benzoyl chloride. Cs2.5Ho.5[PWi204o] showed high efficiency in the acylation of activated arenes, such as p-xylene, anisole, mesitylene, etc., by acetic and benzoic anhydrides and acyl chlorides. This catalyst provided higher yields of acylated arenes than the parent acid H3[PWi204o], the latter being partly soluble in the reaction mixture. ... 

Our recent study ° showed that bulk and silica-supported H3[PWi204o] exhibit a very high activity in the acylation of anisole (Eq. 4) with acetic anhydride in liquid phase, yielding up to 98% para and 2 - 4% ortho isomer of methoxyacetophenone (MOAP) at 70 - 110"C and an anisole to acetic anhydride molar ratio AN/AA = 10-20 (Table 1). 

---