Anisole acylation acyl chlorides

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-... 

In exceptional circumstances the acylium ion (or the polarised complex) can decompose to give an alkyl cation so that alkylation accompanies acylation. This occurs in the aluminium chloride-catalysed reaction of pivaloyl chloride which gives acylation with reactive aromatics such as anisole, but with less reactive aromatics such as benzene, the acylium ion has time to decompose, viz. 

If R is tertiary, RCOmay lose CO to give R, so that the alkylarene ArR is often a side product or even the main product. This kind of cleavage is much more likely with relatively unreactive substrates, where the acylium ion has time to break down. For example, pivaloyl chloride (McaCCOCl) gives the normal acyl product with anisole, but the alkyl product MesCPh with benzene. In the other mechanism an acyl cation is not involved, but the 1 1 complex attacks directly. 

Scheme 1 Acylation of anisole with acetyl chloride...

Acylation of aromatic ethers in the presence of a variety of metal chlorides and oxides [52]. The rate enhancement was probably caused by large temperature gradients but was not evaluated quantitatively. Reaction conditions a single-mode stirred tank reactor, fourfold excess of anisole, no solvent. 

Friedeb Crafts reaction Anisole undergoes Friedel-Crafts reaction, i.e., the all rl and acyl groups are introduced at ortho and para positions by reaction with alkyl halide and acyl halide in the presence of anhydrous alurntnlurn chloride (a Lewis acid) as catalyst. 

The ionic liquids made of ferric chloride and tin chloride displayed good properties as alternative catalysts in the acylation reactions (127). For the acylation of mesitylene with acetylchloride and for the acylation of anisole with acetylanhydride, the best results were obtained with a ferric chloride-containing ionic liquid. The conversions were much higher, and the selectivity obtained was in the same range relative to those observed with the Al- and Sn-chloride-containing ionic liquids. 

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). 

As reported in the literature, the acylation of aromatic hydrocarbons can be carried out by using zeolites as catalysts and carboxylic acids or acyl chlorides as acylating agents. Thus toluene can be acylated by carboxylic acids in the liquid phase in the presence of cation exchanged Y-zeolites (ref. 1). The acylation of phenol or phenol derivatives is also reported. The acylation of anisole by carboxylic acids and acyl chlorides was obtained in the presence of various zeolites in the liquid phase (ref. 2). The acylation of phenol by acetic acid was also carried out with silicalite (ref. 3) or HZSM5 (ref. 4). The para isomer has been generally favoured except in the latter case in which ortho-hydroxyacetophenone was obtained preferentially. One possible explanation for the high ortho-selectivity in the case of the acylation of phenol by acetic acid is that phenylacetate could be an intermediate from which ortho-hydroxyacetophenone would be formed intramolecularly. 

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. 

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... 

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

Scheme 6.10 Montmoril Ionite I<10—Fe (111) as reusable catalyst for the quantitative acylation of anisole by p-nitrobenzoyl chloride.

A global electrophilicity index of common benzylating and acylating agents has been established from MO calculations and it shows a quantitative linear correlation with the experimental substrate selectivity index from a series of benzylation and acylation reactions.21 The values of relative rate coefficients predicted from the index may be accurate to within 10%. The reaction of /-butyl chloride with anisole catalysed by /Moluenesulfonic acid in supercritical difluoromethane has been subject to kinetic analysis.22 The proportions of substitution at the ortho -position and disubstitution increase at lower pressures, attributed to the decrease in the hydrogen-bonding ability of the solvent. 

A recent article reported the use of strongly acidic mesoporous aluminosilicates prepared from zeolite seeds in the acylation of anisole with octanoyl chloride.[30] The mesoporosity improving the transport of the reactants and the presence of strong acid sites lead to high conversion (>90 %) and high selectivity (100 %). 

Shih, P.-C., Wang, J.-H., Mou, C.-Y. Strongly acidic mesoporous aluminosilicates prepared from zeolite seeds acylation of anisole with octanyl chloride, Catal. Today, 2004, 93-95, 365-370. 

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. 

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. 

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... 

Acylation of aromatic ethers yields the corresponding keto ethers. Typical examples are found in the conversion of anisole with aluminum chloride and appropriate acyl halide to p-methoxybutyrophenone (85%) and p-methoxyphenyl benzyl ketone (84%). Mild catalysts like iodine and phosphorus pentoxide are also effective. 

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