Para-acylated product

The liquid phase Friedel-Crafts acylation of thioanisole with iso-butyric anhydride to produce 4-methyl thiobutyrophenone has been studied using supported silicotungstic acid catalysts. Reaction is rapid, giving the para-acylation product in high yield. Reactions have been performed in both batch slurry and trickle bed reactors. In both reactors catalyst deactivation due to strong adsorption of product was observed. 

The activity of 42%STA/silica catalysts for the acylation of related aromatic reactants with iso-butyric anhydride was investigated. In the presence of anisole and veratrole, 100% anhydride conversion was observed, leading to the expected para-acylation products. No reaction was observed in the presence of chlorobenzene and other deactivated aromatic systems. 

Intramolecular Friedel-Crafits acylation can be used to make rings. Use Spartan-Build to build and minimize the ortho, meta, and para acylation products from the following reaction. Which product has the lowest strain energy How do the highen energy isomers reveal the presence of strain ... 

Acetic anhydride and aluminum chloride in caibon disulfide gives a high yield of the para-acylated product with thioanisole, and in dichloromethane the same reagents give an almost quantitative yield of 3-acetyl-1-benzenesulfonylindole. Acylation of more nucleophilic heterocycles can be achieved using milder catalysts, such as zinc chloride. It has been known for some time that furan can be acylated very efficiently using acetic anhydride and zinc chloride. The Paal-Knorr furan synthesis (1,4-diketone, acetic anhydride and zinc chloride) can sometimes result in acylation as well as cyclization (equation 40). - Equations (41) and (42) further exemplify the acylation of furan derivatives that have been used in the synthesis of cytotoxic furanonaphthoquinones. 

If the acylation of toluene with acetic acid depicted above [8] failed, use of the more active acyl chlorides instead of acids and La-exchanged Y-zeolite leads to the para-acylated product [20],... 

Acetylation of the benzene nuclei of a number of l-phenyldicarba-cto o-dodecabor-anes [e.g. (21)] by acetyl chloride in the presence of ttifluoromethanesulfonic acid gave mainly para-acylated products in spite of the strongly electron-withdrawing effect of the carborane skeleton. Substitution of a methyl group at the 2-position of the carborane ring caused acetylation mainly at the meta position. 

As expected, the para-acylated ketone 3 is the major reaction product, with only minor yields of the ortho-acylated product formed. Reaction is very rapid and complete conversions are obtained. Catalyst TOP numbers are >19000h under these conditions. Enolisation and further reaction with the anhydride results in formation of the vinyl ester. Minor amounts of diacile and side products are formed. Similar performances are observed with both supported and nonsupported ST A (at equivalent ST A loading in reactor). Use of nonsupported ST A resulted in agglomeration and deposition of the material onto the reactor wall, whereas the silica supported material could be readily removed by filtration. 

The results reported in this paper show that supported STA catalysts are efficient catalysts for the acylation of thioanisole and related activated aromatic molecules in the presence of iso-butyric anhydride as the acylating agent. The para- substituted ketone isomer is the major acylation product. Optimal catalyst activity is in the range of 60°C to 90°C. Use of either lower STA concentrations or use of weaker acids eg phosphoric acid, decreases the reaction rate and selectivity this results in greater hydrolysis of the anhydride. Use of supported STA catalysts is more efficient than bulk STA since the reaction medium is much cleaner and enables easier removal of the catalyst. 

The main product, C, comes from the addition of both these electrophiles, but which adds first The ketone in A is meta-directing but the t-butyl group in B is para-directing. Product C has a par. relationship and must come from Friedel-Crafts acylation of B with the acylium cation. 

In the preparation of mixed carboxylic-perfluoroalkane sulfonic anhydrides from the corresponding acids, water formahon is responsible for the low yields of the acylation product. By removing water from the reaction mixture by azeotropic distillation and adsorption onto molecular sieves, the yield of benzoylahon of para-xylene with BAC in the presence of perfluorobutanesulfonic acid (10% mol) is improved to 90%. 

Para-acetylation of anisole with AAN is performed in the presence of ytterbium triflate (20% mol). The reaction proceeds smoothly even when the catalyst is employed in a small amount (5% mol), and the desired acylation product is obtained in 79% yield. Several substituted benzenes are subjected to ytterbium-triflate-catalyzed acetylation. Though acetylation of benzene does not occur, introduction of a methylthio or dimethylamino group on the aromatic ring gives the acylation products in high yields. The presence of a methyl group is less effective, and mete-xylene is acy-lated to 2,4-dimethylacetophenone in only 25% yield. Ytterbium triflate can be recovered from the aqueous layer by simple extraction and reused for two additional runs in the model acetylation of anisole, affording para-acetylanisole with almost the same yield as in the first use. 

Interestingly, in the presence of graphite or para-toluenesulfonic acid alone, no acylated products are isolated. The effect of the solvent is detrimental since only traces of the products are detected when the reactions are carried out in methylene chloride or chloroform. It must be underlined that graphite can be reused after simple washing with ethyl acetate and water, but the para-toluenesulfonic acid, which is not adsorbed on the graphite during the reaction, must be added again for the successive runs. 

The production of aromatic hydroxyketones can also be performed by the Fries rearrangement in this case, the mode of para-acylation is probably different from that of ortho-acylation. Indeed, the ortho-isomer is a primary product, whereas the para-isomer seems to be a secondary product. Of course, other methods for... 

Dealumination of the ZSM-5 zeolite shows a great effect on ortho/ para selectivity in the acylation of phenol by AAC. Thus, for a phenol conversion of 20%, ortho/para selectivity is 7.0 when ZSM-5(41.8) is utilized, and becomes 13.0 in the presence of ZSM-5(42.4). This unexpected increase in the ortho/para ratio can only be explained by postulating that ortho-HAP and para-HAP result from different pathways. The ortho isomer is mainly produced in the pores, whereas para isomer production occurs only on the external acid sites. The ortho isomer can be formed by direct C-acylation of phenol with AAC this selective reaction can be related to the general mechanism reported in Scheme 5.1. ortho-HAP can also be obtained by the Fries rearrangement. On the contrary, the para-isomer is a secondary product and, therefore, it results from the acylation of phenol by PA according to Scheme 5.6. 

Unmodified BEA zeolite, on the other hand, shows the highest activity in the acylation of phenol wifh benzoic anhydride. Phenyl benzoate (PB) is the main product (61% yield), accompanied by C-acylated products (35%), with an interesting para-selectivity (ortho/para = 0.48). When the reaction time is increased from 4 to 20 h, an increase in para-hydroxy-benzophenone yield (from 11% to 23%) fogefher wifh a decrease in PB yield (from 79% to 64%) is observed however, a small increase in the orf/zo-hydroxybenzophenone yield (from 9% to 10%) cannof be avoided. The acfivify of the catalyst, together with its selectivity, does not distinctly decrease when the catalyst is used from fresh to firsf recycle. 

Phenol undergoes propanoylation with propanoyl chloride over BEA, Y, MOR, and ZSM-5 zeolites The main product is phenylpropanoate moreover, BEA (Scheme 5.7) is the most active in the C-acylation and selective for para-hydroxypropiophenone production (ortho/para = 0.53) compared to other zeolite catalysts. 

Gauthier et al. (1989) studied the activity of various cation-exchanged Y-type zeolites in the acylation of toluene with octanoic acid, obtaining selectivities to the para isomer of 94% at 75% yield of acylated product. The most efficient catalysts were rare-earth-exchanged zeolites (70% exchange), the following order of activity being observed Cr3+, Zr4+ < M2+, Cu2+, Co2+ <11 < Pr3+, La3+, Gd3+, Yb3+, Ce3+. 

The acylation of anisole with C2 - C12 acids was carried out under the same conditions as that of toluene, except a shorter reaction time (5 h). The acylated anisole formed as the major product para/ortho = 59 1 - 96 1 and no meta isomers) together with esterification products - methyl esters of carboxylic acids and phenol. No phenyl esters formed. The selectivity to esters increases from acetic to dodecanoic acid, reaching 40% for the latter. The acylation of anisole, in contrast to that of toluene, is most efficient with C2 - C6 acids, giving a 62 - 65% yield of acylated products and only 2 - 6% of methyl esters. 

R - C = 0. Once formed, the acylium ion undergoes an electrophilic aromatic substitution reaction with the aromatic compound. The product of this acylation reaction is an aromatic ketone. Toluene is acylated by propanoyl chloride to give both ortho and para substituted products. 

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