Acyl chlorides aromatic compound reactions with

Triflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Fnedel-Crafis catalysis for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides m the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the triflates in comparison with the correspond mg fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

The classes of compounds which are conveniently considered together as derivatives of carboxylic acids include the carboxylic acid anhydrides, acyl chlorides, esters, and amides. In the case of simple aliphatic and aromatic acids, synthetic transformations among these derivatives are usually a straightforward matter involving such fundamental reactions as ester saponification, formation of acyl chlorides, and the reactions of amines with acid anhydrides or acyl chlorides ... 

An acyl group, -COR (pronounced a-sil), is introduced onto the ring when an aromatic compound reacts with a carboxylic acid chloride, RCOCl, in the presence of AICI3. For example, reaction of benzene with acetyl chloride yields the ketone, acetophenone. 

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. 

The most important method for the synthesis of aromatic ketones 3 is the Friedel-Crafts acylation. An aromatic substrate 1 is treated with an acyl chloride 2 in the presence of a Lewis-acid catalyst, to yield an acylated aromatic compound. Closely related reactions are methods for the formylation, as well as an alkylation procedure for aromatic compounds, which is also named after Friedel and Crafts. 

Diaryl sulfones can be formed by treatment of aromatic compounds with aryl sulfonyl chlorides and a Friedel-Crafts catalyst. This reaction is analogous to Friedel-Crafts acylation with carboxylic acid halides (11-14). In a better procedure, the aromatic compound is treated with an aryl sulfonic acid and P2O5 in polypho-sphoric acid. Still another method uses an arylsulfonic trifluoromethanesulfonic anhydride (ArS020S02CF3) (generated in situ from ArS02Br and CF3S03Ag) without a catalyst. ... 

In another nonelectrolytic process, arylacetic acids are converted to vi c-diaryl compounds 2A1CR2COOH —> ArCR2CR2Ar by treatment with sodium persulfate (Na2S20g) and a catalytic amount of AgNOs." Both of these reactions involve dimerization of free radicals. In still another process, electron-deficient aromatic acyl chlorides are dimerized to biaryls (2 ArCOCl —> ArAr) by treatment with a disilane RsSiSiRs and a palladium catalyst." " ... 

Other than energy considerations, on which there is little comparative data, the most important green role for photochemistry is in improving atom economy. Although only a preliminary research result, an excellent example of this is the avoidance of the need for stoichiometric amounts of Lewis acid catalysts in the synthesis of some acylated aromatic compounds. Benzoquinone can be reacted with an aldehyde under a sunlamp to yield an acylhydroquinone in up to 88% yield. The alternative procedure would involve reaction of an acyl chloride with hydroquinone and a... 

Mesylates are used for Ni-catalysed reactions. Arenediazodium salts 2 are very reactive pseudohalides undergoing facile oxidative addition to Pd(0). They are more easily available than aryl iodides or triflates. Also, acyl (aroyl) halides 4 and aroyl anhydrides 5 behave as pseudohalides after decarbonylation under certain conditions. Sulfonyl chlorides 6 react with evolution of SO2. Allylic halides are reactive, but their reactions via 7t-allyl complexes are treated in Chapter 4. Based on the reactions of those pseudohalides, several benzene derivatives such as aniline, phenol, benzoic acid and benzenesulfonic acid can be used for the reaction, in addition to phenyl halides. In Scheme 3.1, reactions of benzene as a parent ring compound are summarized. Needless to say, the reactions can be extended to various aromatic compounds including heteroaromatic compounds whenever their halides and pseudohalides are available. 

Bottom reaction (as a reminder) chemoselective acylation of an aromatic compound with an activated carboxylic chloride (Friedel-Crafts acylation, cf. Section 5.2.7). 

The reaction of an aromatic compound with an acyl chloride in the presence of a Lewis acid (usually A1C13) results in the substitution of an acyl group onto the aromatic ring. An example of this reaction, known as the Friedel-Crafts acylation, is provided by the following equation ... 

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