Aromatics acylation

OF SUBSTITUTED AROMATIC AMIDES (AROMATIC ACYLATED BASES)... 

Aromatic acyl halides and sulfonyl halides undergo oxidative addition, followed by facile elimination of CO and SO2 to form arylpalladium complexes. Benzenediazonium salts are the most reactive source of arylpalladium complexes. 

Since the rate of aliphatic acylation is higher than that of aromatic acylation, the olefin may possess aromatic substituents yields are lower, however, than with aliphatic olefins. Tlie types of olefins with aliphatic or aromatic substituents, undergoing diacylation, are shown in Table I. Systematic variation of the structure of the olefin... 

Primarily hydrolyses esters with longer aliphatic (compared to AChE) or aromatic acyl moiety, such as butyrylcholine (BCh) and benzoylcholine (BzCh). BChE is the primary circulating ChE. It is threefold more abundant than AChE in human blood and is found in liver, lungs, muscles, brain and heart. 

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." " ... 

Wilkinson s catalyst has also been reported to decarbonylate aromatic acyl halides at 180°C (ArCOX ArX). This reaction has been carried out with acyl iodides, bromides, and chlorides. Aliphatic acyl halides that lack an a hydrogen also give this reaction, but if an a hydrogen is present, elimination takes place instead (17-16). Aromatic acyl cyanides give aryl cyanides (ArCOCN—> ArCN). Aromatic acyl chlorides and cyanides can also be decarbonylated with palladium catalysts. °... 

In a similar reaction, aromatic acyl halides are converted to amines in one laboratory step by treatment with hydroxylamine-O-sulfonic acid. " ... 

Coupling of aromatic acyl halides, with decarbonylation... 

Chloroacylation of terminal aryl, alkyl or alkenyl alkynes [Le. the addition of RC(=0)-C1 across the CC triple bond] with aromatic acyl chlorides was catalysed by [IrCl(cod)(lPr)] (5 mol%) in good conversions (70-94%) in toluene (90°C, 20 h). Z-addition products were observed only, hitemal alkynes were umeactive. Surprisingly, a phosphine/[lr(p-Cl)(l,5-cod)]2 system under the same conditions provides decarbonylation products (Scheme 2.34) [117]. 

Ketones can also be prepared by palladium-catalyzed reactions of boranes or boronic acids with acyl chlorides. Both saturated and aromatic acyl chlorides react with trialkylboranes in the presence of Pd(PPh3)4.233... 

Aromatic acyl chlorides also react with arylboronic acids to give ketones.234... 

A special case of aromatic acylation is the Fries rearrangement, which is the conversion of an ester of a phenol to an o-acyl phenol by a Lewis acid. 

The Beta material prepared by seed silanization show interesting catalytic properties in aromatic acylation reaction, especially when using a bulky substrate, such as 2-methoxynaphthalene. The superior activity and selectivity exhibited by this sample has been related to the presence of a hierarchical porosity, which decreases the steric and diffusional hindrances, favoring the accessibility to the active sites and allowing the occurrence of the transacylation reaction. 

Among the wide variety of organic reactions in which zeolites have been employed as catalysts, may be emphasized the transformations of aromatic hydrocarbons of importance in petrochemistry, and in the synthesis of intermediates for pharmaceutical or fragrance products.5 In particular, Friede 1-Crafts acylation and alkylation over zeolites have been widely used for the synthesis of fine chemicals.6 Insights into the mechanism of aromatic acylation over zeolites have been disclosed.7 The production of ethylbenzene from benzene and ethylene, catalyzed by HZSM-5 zeolite and developed by the Mobil-Badger Company, was the first commercialized industrial process for aromatic alkylation over zeolites.8 Other typical examples of zeolite-mediated Friedel-Crafts reactions are the regioselective formation of p-xylene by alkylation of toluene with methanol over HZSM-5,9 or the regioselective p-acylation of toluene with acetic anhydride over HBEA zeolites.10 In both transformations, the p-isomers are obtained in nearly quantitative yield. 

J. J. Scheele, Electrophilic Aromatic Acylation. Tech. Hogesch, Delft, The Netherlands, 1991 Chem. Abstr. 1992, 117, 130844y. 

Condensation of aromatic acyl compounds with N,N-dimethylformamide diethyl acetal in a pressure tube under the action of microwave irradiation affords easy access to l-aryl-3-dimethylaminoprop-2-enones in almost quantitative yield after 6 min. These intermediates can then be reacted with hydrazine hydrate under conventional reflux in ethanol to form the corresponding 3-substituted pyrazoles [95] (Scheme 8.69). 

Acyl nitroso compounds react with 1, 3-dienes as N-O heterodienophiles to produce cycloadducts, which have found use in the total synthesis of a number of nitrogen-containing natural products [21]. The cycloadducts of acyl nitroso compounds and 9,10-dimethylanthracene (4, Scheme 7.3) undergo thermal decomposition through retro-Diels-Alder reactions to produce acyl nitroso compounds under non-oxidative conditions and at relatively mild temperatures (40-100°C) [11-14]. Decomposition of these compounds provides a particularly clean method for the formation of acyl nitroso compounds. Photolysis or thermolysis of 3, 5-diphenyl-l, 2, 4-oxadiazole-4-oxide (5) generates the aromatic acyl nitroso compound (6) and ben-zonitrile (Scheme 7.3) [22, 23]. Other reactions that generate acyl nitroso compounds include the treatment of 5 with a nitrile oxide [24], the addition of N-methyl morpholine N-oxide to nitrile oxides and the decomposition of N, O-diacylated or alkylated N-hydroxyarylsulfonamides [25-29]. 

Aromatic compounds, 13 108-109 13 680. See also Aromatics acylation of, 12 173-181 amination of, 12 184 arylation of, 12 170-171 Cycloalkylation of, 12 169 in diesel fuel, 12 425 formylation of, 12 178 Friedel-Crafts acylation of, 12 174 Friedel-Crafts alkylation of, 12 164 nitration of, 12 182-183 oxidative coupling of, 19 654 sulfonation of, 12 181 sulfonation reagents for, 23 521-524 Aromatic-containing polymers, sulfonation of, 23 535-536... 

Aromatic acyl halides containing a nitro group adjacent to the halide function show a tendency towards violent thermal decomposition. The few individually indexed compounds are ... 

Prodrugs That Incorporate an Aromatic Acyl Pro-Moiety... 

The acyl radicals obtained by hydrogen abstraction from aldehydes easily attack protonated heteroaromatic bases. With secondary and tertiary acyl radicals decarbonylation competes with the aromatic acylation [Eq. (12)]. 

There are solid phase enthalpy of formation data for four aromatic acyl peroxides dibenzoyl peroxide and the bis-o- and bis-p-toluyl derivatives and dicinnamoyl peroxide. The last three were reported in the same publication . The first disconcerting observation is that the p-methyl substituted benzoyl peroxide is less stable than the ortho isomer by nearly 50 kJmol. We cannot reconcile the large difference between the enthalpies of formation of these two isomers, especially since the corresponding anhydrides have comparable enthalpies of formation, —521.0 + 7.9 (p ) and —533.5 + 7.9 (o )kJmol . However, they too exhibit an unexpected stability order and were measured by the same... 

The application of standardized UV (or UV-Vis) spectroscopy has for years been used in analyses of flavonoids. These polyphenolic compounds reveal two characteristic UV absorption bands with maxima in the 240 to 285 and 300 to 550 nm range. The various flavonoid classes can be recognized by their UV spectra, and UV-spectral characteristics of individual flavonoids including the effects of the number of aglycone hydroxyl groups, glycosidic substitution pattern, and nature of aromatic acyl groups have been reviewed in several excellent books. ... 

The UV-Vis spectral data on anthocyanins (typically measured in methanol containing O.OP/o HCl) give important information about the nature of the aglycone and aromatic acyl... 

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