Acylation aromatic

Friedel-Crafts acylation of aromatic compounds (Section 12 7) Acyl chlorides and carboxylic acid anhydrides acylate aromatic rings in the presence of alumi num chloride The reaction is electrophil ic aromatic substitution in which acylium ions are generated and attack the ring... 

Acylation. Aromatic amines react with acids, acid chlorides, anhydrides, and esters to form amides. In general, acid chlorides give the best yield of the pure product. The reaction with acetic, propionic, butanoic, or benzoic acid can be catalyzed with phosphoms oxychloride or trichloride. 

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. 

Cefotiam (67) has an acyl aromatic C-7 side chain bioisosteric with an anilino ring. It can be prepared by... 

Friedel-Crafts acylation reaction and,557-558 resonance in, 558 Acyl group, 557, 686 names of, 753 Acyl phosphate, 816 naming, 788 Acylation (aromatic), see... 

Rearrangement of N-halo-N-acyl aromatic amines (Orton)... 

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... 

Reaction conditions reflux of a mixture of the aromatic compound, N-benzoylimid-azole, and trifluoroacetic acid in a molar ratio of 1 1.2 10. This method for acylating aromatic hydrocarbons works without the use of classical Friedel-Crafts catalysts. 

Heating dicarboxylic acids, HOOC(CH,) COOH n = 2 or 3), forms cyclic anhydrides by intramolecular dehydration [Problem 16.22(a), (6)]. Anhydrides resemble acid halides in their reactions. Because acetic anhydride reacts less violently, it is often used in place of acetyl chloride. Acid anhydrides can also be used to acylate aromatic rings in electrophilic substitutions. 

Aromatic nitroso compounds combine with primary arylamines in glacial acetic acid to give symmetrical or unsymmetrical azo compounds (the Mills reaction).554 A wide variety of substituents may be present in both aryl groups. Unsymmetrical azo compounds have also been prepared by the reaction between aromatic nitro compounds ArN02 and N-acyl aromatic amines Ar NHAc.555 The use of phase transfer catalysis increased the yields. 

More recent studies reconfirmed the excellent properties of these acylating systems and showed that aroyl triflates are able to acylate aromatics without catalysts... 

Carboxybenzyl aryl ketones are formed together with the isocoumarin when homophthalic anhydride (isochroman-l,3-dione) is used to acylate aromatic molecules under Friedel-Crafts conditions (51JOC1064) and the 7-methoxy derivative behaves in a similar fashion (66JIC615). Some care in the choice of Lewis acid is necessary in view of the formation of the tropone derivative (504) in the acylation of hydroquinone (Scheme 181) (55JCS2244). 

Chymotrypsin, a serine endopeptidase, most readily reacts at the carboxyl group of the aromatic amino acid residue of proteins and polypeptides (or N-acyl aromatic amino acid esters) to form first a tetrahedral intermediate which then collapses into an acyl-enzyme (7+ 8- I>). The acyl-enzyme is then hydrolyzed by water to furnish the M-acylated aromatic amino acid again through the formation of a tetrahedral intermediate (JO Jl -> J2) (1-4). 

As discussed in Chapter 2, Shudo and Ohwada found that acetyl and benzoylhexafluoroantimonate salts (CH3CO+SbF6 and CfiHsCO+SbFf,-, respectively) acylate aromatic compounds with increasing reaction rates and greater yields in progressively more acidic media.44 These data are consistent with the formation of the superelectrophilic species 137 and 141 (eq 39).65... 

Acylation. Aromatic acyclation processes are widely applied in the fine chemical industry as reaction steps in the synthesis of pharmaceuticals and fragrances. Present day industrial synthesis generally involves acid chlorides as the acylating agent. Due to the strong coordination of the product ketone to the Lewis-acid "catalyst" (A1C13,... 

Similarly, a series of m- and -substituted anilides 68 of thienoic acid were prepared and their H NMR spectroscopic characteristics were examined. In general, good correlations were observed between the chemical shifts of proton signals of the acyl aromatic rings and the Hammett . 

PhI(OTf)2, NaI04, peroxyacetic acid, H2O2 peroxydisulfates, and ammonium iodide with Oxone . The ICl is a better iodinating agent than iodine itself. Among other reagents used have been IF (prepared directly from the elements), and benzyltrialkylammonium dichloroiodate (which iodinates phenols, aromatic amines, and A-acylated aromatic amines, as well... 

Friedel-Crafts acylation. Aromatic acylation is generally effective with ZrO as catalyst. Thus, aniline is converted to 4-acetaminoacetophenone in 65% yield. 

The mechanism described in Section 4.7(b) Group 13 Lewis acids involves the abstraction of CL from CHjCOCl by AlClj to form AICL and the Lewis acid CHjCO" (an acylium cation). This cation then attacks benzene to form the acylated aromatic product. An alumina surface, such as the partially dehydroxylated one shown below, would also provide Lewis acidic sites that could abstract CT ... 

F. Minisci, F. Recupero, A. Cecchetto, C. Gambarotti, C. Punta, R. Paganelli, G. F. Pedulli, F. Fontana, Solvent and temperature effects in the free radical aerobic oxidation of alkyl and acyl aromatics catalysed by transition metal slats and N-hydroxyphatUmide New processes for the sysnthesis of p-hydroxybenzoic acid, diphenols, and dienes liquid for liquid crystals and cross-linked polymers, Org. Proc. Res. Devel. 8 (2004) 163. 

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