Anisole, Friedel-Crafts acylation

The ability of iron(III) chloride genuinely to catalyze Friedel-Crafts acylation reactions has also been recognized by Holderich and co-workers [97]. By immobilizing the ionic liquid [BMIM]Cl/FeCl3 on a solid support, Holderich was able to acetylate mesitylene, anisole, and m-xylene with acetyl chloride in excellent yield. The performance of the iron-based ionic liquid was then compared with that of the corresponding chlorostannate(II) and chloroaluminate(III) ionic liquids. The results are given in Scheme 5.1-67 and Table 5.1-5. As can be seen, the iron catalyst gave superior results to the aluminium- or tin-based catalysts. The reactions were also carried out in the gas phase at between 200 and 300 °C. The acetylation reac-... 

Thioacetals eliminate to vinylsulfides in the presence of CuOTf (Scheme 46).192 Cu1 and Cu11 triflates are mild Lewis acids for Friedel-Crafts acylation and alkylation reactions. CuOTf effectively catalyzes the reaction of anisole with selenoesters.193,194 Copper(II) sulfate promotes epoxide ring opening reactions in the presence of pyridine,195 with retention of configuration being observed. Cu(OTf)2 is a catalyst for the ring opening of aziridine by aniline.196... 

Friedel-Crafts acylation is widely used for the production of aromatic ketones applied as intermediates in both fine chemicals and pharmaceutical industries. The reaction is carried out by using conventional homogenous catalysts, which represents significant technical and environmental problems. The present work reports the results obtained in the Friedel-Crafts acylation of aromatic substrates (anisole and 2-methoxynaphthalene) catalyzed by Beta zeolite obtained by crystallization of silanized seeds. This material exhibits hierarchical porosity and enhanced textural properties. For the anisole acylation, the catalytic activity over the conventional Beta zeolite is slightly higher than with the modified Beta material, probably due to the relatively small size of this substrate and the weaker acidity of the last sample. However, the opposite occurred in the acylation of a bulky substrate (2-methoxynaphthalene), with the modified Beta showing a higher conversion. This result is interpreted due to the presence of a hierarchical porosity in this material, which favors the accessibility to the active sites. 

In the Mukaiyama aldol additions of trimethyl-(l-phenyl-propenyloxy)-silane to give benzaldehyde and cinnamaldehyde catalyzed by 7 mol% supported scandium catalyst, a 1 1 mixture of diastereomers was obtained. Again, the dendritic catalyst could be recycled easily without any loss in performance. The scandium cross-linked dendritic material appeared to be an efficient catalyst for the Diels-Alder reaction between methyl vinyl ketone and cyclopentadiene. The Diels-Alder adduct was formed in dichloromethane at 0°C in 79% yield with an endo/exo ratio of 85 15. The material was also used as a Friedel-Crafts acylation catalyst (contain-ing7mol% scandium) for the formation of / -methoxyacetophenone (in a 73% yield) from anisole, acetic acid anhydride, and lithium perchlorate at 50°C in nitromethane. 

Seddon and coworkers studied the Friedel-Crafts acylations of toluene, chlorobenzene and anisole with acetyl chloride in [emim][Al2Cl7] and obtained excellent regioselectivities to the para isomer, Scheme 9. Similarly, the fragrance chemical, traseolide, was obtained in 99% yield as a single isomer. Scheme 10. It should be noted, however, that the question of product recovery from the reaction medium still needs to be addressed in these systems. 

The exceedingly high reactivity of ferrocene to Friedel-Crafts acylation is exemplified by the fact that mild catalysts such as stannic chloride (63), boron trifluoride (32), zinc chloride (86), and phosphoric acid (29), can be used with considerable success. When ferrocene and anisole were allowed to compete for limited amounts of acetyl chloride and aluminum chloride, acetylferrocene was the sole product isolated, again illustrating the high reactivity of ferrocene toward electrophilic reagents (6). 

Monodirectional 12 membered ring zeolites (offretite, L, mordenite and 0) are very inefficient as catalysts for formaldehyde benzene condensation to give diphenylmethane, esterification of phenylacetio acid with equimolar amounts of ethanol, Friedel-Crafts acylation of 3-phenylpropanoyl chloride with anisole and Claisen-Schmidt condensation of acetophenone with benzaldehyde. This fact has been attributed to diffusional constraints of organic compounds inside the channels. By contrast, the behaviour of the tridireotional f zeolite is very similar to that of dealuminated HY zeolites, inoreasing the turnover of the acid sites with the framework Si-to-Al ratio. 

Friedel-Crafts acylation of 3-phenylpropanoyl chloride (0.59 mmol) in anisole (50 ml) at 408 K in the presence of acid zeolites (1,00 g) for 17 h of reaction time. 

Nafion-silica nanocomposite catalysts have also been tested in the Friedel-Crafts acylation of aromatics with acyl chlorides.191,194,371 Anisole, toluene, and... 

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... 

In the RE(OTf)3-catalyzed Friedel-Crafts acylation, the acylation of aromatic compounds with electron-donating substituents, for example anisole and mesity-lene, proceeded smoothly whereas the reactivity of benzene, toluene, and xylenes was low under the same conditions. On the other hand, it was revealed that the catalyst activity of RE(OTf)3 was increased when combined with LiC104, and that the acceleration effect was strongly dependent on the amount of LiC104. 

Draw a mechanism for the acylation of anisole by propionyl chloride. Recall that Friedel-Crafts acylation involves an acylium ion as the electrophile in electrophilic aromatic substitution. 

As would be expected, high rate accelerations can result when reactions proceeding through ionic intermediates, e.g. carbocations, are performed in ionic liquids. For example, Seddon and coworkers [100] studied the Friedel-Crafts acylation of toluene, chlorobenzene (Fig. 7.30) and anisole with acetyl chloride in [emi-m][Al2Cl7], whereby the ionic liquid is acting both as solvent and catalyst. They ob-... 

Several metal triflate salts have been tested in the Friedel-Crafts acylation of anisole with benzoyl chloride in [C4Ciim][BF4]. At a reaction temperature of 80°C and catalyst loadings of 10 mol%, all salts led to 100% conversion with reaction rates decreasing in the order Cu(OTf)2 > Zn(OTf)2 > Sn(OTf)2 Sc(OTf)3, see Scheme 9.22.[92]... 

The Friedel-Crafts acylation of toluene, chlorotol-uene, and anisole with acetyl chloride in [emim] [C1]/A1C13 gives excellent regioselectivities to the... 

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]. 

Selvin, R., Sivasankar, B., Rengaraj, K. Kinetic studies on Friedel-Crafts acylation of anisole by clayzic. React. Kinet. Catal. Lett. 1999, 67, 319-324. 

Iodine in trace amounts has been used as catalyst in Friedel-Crafts acylations of furane and thiophene and of more active members of the benzene series such as anisole and acetanilide. " Oddly enough, it is not effective for benzoylation of anthracene.""... 

Table 2.9 Comparison of the Friedel-Crafts acylation of anisole using AICI3 (liquid phase) and H-Beta (heterogeneous).

---