Anhydrides with aromatic rings

Friedel-Crafts acylation involves the direct introduction of an acyl group on the aromatic rings. This reaction, when carried out using corrosive and liquid catalysts, poses tedious workup and separation problems. An effort to minimize such limitations was made by Alizadeh et al. (2007), who reported a Friedel-Crafts reaction involving the treatment of acetic anhydride with aromatic compounds in the presence of SSA as a reusable, nontoxic, and heterogeneous catalyst (Scheme 5.44). 

Acyl cations (acylium ions) generated by treating an acyl chloride or acid anhydride with aluminum chloride attack aromatic rings to yield ketones The arene must be at least as reactive as a halobenzene Acyl cations are relatively stable and do not re arrange... 

Acylatmg agents such as acyl chlorides and carboxylic acid anhydrides can react with phenols either at the aromatic ring (C acylation) or at the hydroxyl oxygen (O acylation)... 

TBPA is prepared in high yield by the bromination of phthalic anhydride in 60% oleum (51). The use of oleum as the bromination solvent results in some sulfonation of the aromatic ring (52). Sulfonated material is removed by hydrolyzing the anhydride with dilute NaOH, filtering and acidifying with dilute HCl. The precipitated acid is washed several times with hot water and reconverted to the anhydride by heating at 150°C for several hours. 

Trimelhtate Esters. These materials are produced by the esterification of a range of alcohols with trimeUitic anhydride (TMA), which is similar ia stmcture to phthaHc anhydride with the exception of the third functionaHty (COOH) on the aromatic ring. Consequendy, esters are produced ia the ratio of three moles of alcohol to one mole of anhydride. Common esters ia this family are tris-2-ethyhexyl trimeUitate (trioctyl trimeUitate, TOTM) L79TM, an ester of mixed semilinear C and C alcohols and L810TM, an ester of mixed linear Cg and C q alcohols. 

Poly(phenylene oxide)s undergo many substitution reactions (25). Reactions involving the aromatic rings and the methyl groups of DMPPO include bromination (26), displacement of the resultant bromine with phosphoms or amines (27), lithiation (28), and maleic anhydride grafting (29). Additional reactions at the open 3-position on the ring include nitration, alkylation (30), and amidation with isocyanates (31). 

Aromatic Ring Reactions. In the presence of an iodine catalyst chlorination of benzyl chloride yields a mixture consisting mostly of the ortho and para compounds. With strong Lewis acid catalysts such as ferric chloride, chlorination is accompanied by self-condensation. Nitration of benzyl chloride with nitric acid in acetic anhydride gives an isomeric mixture containing about 33% ortho, 15% meta, and 52% para isomers (27) with benzal chloride, a mixture containing 23% ortho, 34% meta, and 43% para nitrobenzal chlorides is obtained. 

A Methylanthrapyridone and Its Derivatives. 6-Bromo-3-methylanthrapyridone [81-85-6] (75) is an important iatermediate for manufacturiag dyes soluble ia organic solvents. These solvent dyes are prepared by replacing the bromine atom with various kiads of aromatic amines. 6-Bromo-3-methylanthrapyridone is prepared from 1-methyl amino-4-bromoanthra quin one (43) by acetylation with acetic anhydride followed by ring closure ia alkaU. The startiag material of this route is anthraquiaoae-l-sulfonic acid (16). 

Tractable polymers can be prepared when amino and anhydride functions are not located on the same aromatic ring, and different strategies were employed to obtain soluble polymer. AB benzhydrol imide was prepared by polycondensation of 4-(3-amino-l-hydroxymethylene) phtlialic acid monomethyl ester in NMP. The polymer soluble in NMP has been used as adhesive and coating.56 A second approach was based on an ether imide structure. AB aminophenylether phthalic acids (Fig. 5.34) were prepared by a multistep synthesis from bisphenols.155 The products are stable as hydrochloride, and the polycondensation takes place by activation with triphenylphosphite. The polymers are soluble in an aprotic polar... 

Ohwada extends his theory, unsymmetrization of n orbitals, to Orbital Phase Environment including the secondary orbital interaction (Chapter Orbital Phase Environments and Stereoselectivities by Ohwada in this volume). The reactions between the cyclopentadienes bearing spiro conjugation with benzofluorene systems with maleic anhydride exemplified the importance of the phase environment. The reactions proceed avoiding the out-of-phase interaction between dienophile LUMO and the HOMO at the aromatic rings. The diene 34 with benzo[b]fluorene favored syn addition with respect to the naphtalene ring, whereas the diene 35 with benzo[c]fluorene showed the reverse anti preference (Scheme 22) [28]. 

Silica sol-gel inunobihzed La(OTf)3 (Scheme 48.2B) previously used in the acylation of a series of alcohols and activated aromatic compounds using acetic anhydride as acylating agent, showed a poor activity compared with other various sihca sol-gel inunobihzed triflate derivatives (tert-butyl-dimethylsilyl-trifluoromethane-sulfonate (BDMST), or trifhc acid (HOTf)). Acylation at the aromatic ring occurred over the BDMST and HOTf catalysts, while the La(OTl)3 catalysts only led to O-acetylated products [22]. Such behavior is characteristic... 

Nitroimidazoles substituted by an aromatic ring at the 2-position are also active as antitrichomonal agents. Reaction of p-fluorobenzonitrile (83) with saturated ethanolic hydrogen chloride affords imino-ether 84. Condensation of that intermediate with the dimethyl acetal from 2-aminoacetaldehyde gives the imidazole 85. Nitration of that heterocycle with nitric acid in acetic anhydride gives 86. Alkylation with ethylene chlorohydrin, presumably under neutral conditions, completes the synthesis of the anti-... 

Conversion of MEM ethers to esters. 2-Methoxyethoxymethyl (MEM) ethers are converted into carboxylic esters by reaction with an anhydride in the presence of FeCl3 (0.4 equiv.) (equation I). Selective cleavage is possible in the presence of a benzyl ether but not in the presence of a f-butyl ether. Aromatic rings, if present, can undergo acylation. 

The mixed anhydride method was used with diaminoethane to give a free amino group that was subsequently reacted with 4-hydroxybenzoic acid to provide an aromatic ring to allow iodination with [ ] to increase sensitivity of the assay compared with labelled radioactive tracers. This reaction could also be used to prepare fluorescent compounds for cell-biology studies. 

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