Aroyl group

The large class of antiinflammatory phenylacetic acids are treated at some length in Chapter 4. A number of these agents consist of acetic or propionic acids substituted "by an aroyl group. It is of interest that the central benzene ring of these molecules can be replaced by pyrrole with retention of activity. 

Itahara has also found that the phenylation of A-aroylpyrroles can be achieved using Pd(OAc>2 [30, 31]. Although A-benzoylpyrrole (22) yields a mixture of diphenylpyrrole 23, cyclized pyrrole 24, and bipyrrolyl 25 as shown, l-(2,6-dichlorobenzoyl)pyrrole 26 gives the diphenylated pyrrole 27 in excellent yield. The IV-aroyl groups are readily cleaved with aqueous alkali and the arylation reaction also proceeds with p-xylene and p-dichlorobenzene. Unfortunately, N-methyl-, iV-acetyl-, and A-(phenoxycarbonyl)pyrroles give complex mixtures of products. 

The propenyl group can then supply electrons to the cobalt atom by a resonance effect. This basic mechanism may also be applied to explain the marked accelerating effect of the aroyl group. Except in cases where ortho substitution sterically hinders formation of a cyclic transition state substitution on the aromatic ring has relatively little effect on the rate of decomposition. 

Introduction of an electron-withdrawing substituent Y into the aroyl group on the nitrogen atom shifts the equilibrium 75A 75B (R = Me ... 

Introduction of an electron-withdrawing substituent X onto the aroyl group of aroylacetone A-benzoylhydrazone 75 (R = Me R = H R = XC6H4 R = Ph), as anticipated, shifts the equilibrium toward the cyclic tautomer ... 

Z 75A- . 8mall amounts of the cyclic pyrazoline tautomer were detected only for derivatives containing strongly electron-withdrawing substituents X. Electron-withdrawing substituents Y on the A-aroyl group shift the equilibria 75A - 75A -Z 75A- [( 03)280] slightly in favor of the... 

The isomerization between N- and (9-acylated benzotriazol-l-ols and 1,2,3-triazol-l-ols has been extensively studied (see Section 4.01.7.1) in part by x-ray methods. The aroyl group position is established by x-ray crystallographic analyses because the N- and (9-acylated forms are not readily distinguished by spectral methods. X-ray analyses of l-(4-nitrobenzoyloxy)-1,2,3-triazole (19a) <93AX(C)49>, l-(4-chlorobenzoyloxy)-l,2,3-triazole (19b) <88AX(C)1063>, and 1-benzoyloxy-... 

Since formamide is a weak nucleophile, the use of imidazole or 4-dimethylaminopyridine (DMAP) is necessary for acyl transfer to formamide via an activated amide (imidazolide) or acylpyridinium ion. As Scheme 22 illustrates, the reaction starts with the oxidative addition of aryl bromide 152 to Pd(0) species, followed by CO insertion to form acyl-Pd complex 154. Imidazole receives the aroyl group to form imidazolide 155 and liberates HPdBr species. Then, imidazolide 155 reacts with formamide to form imide 156. Finally, decarbonylation of imide 156 gives amide 157. In fact, the formations of imidazolide intermediate 155 and imide 156 as well as the subsequent slow transformation of imide 156 to amide 157 by releasing CO were observed. This mechanism can accommodate the CO pressure variations observed during the first few hours of aminocarbonylation. When the reaction temperature (120 °C) was reached, a fast drop of pressure occurred. This corresponds to the formation of the intermediary imide 156. Then, the increase of pressure after 3 h of reaction was observed. This phenomenon corresponds to the release of CO from imide 156 to form amide 157. ... 

Mattice37 observed the photorearrangement of 3,4-benzocumarin (78) to 4-hydroxyfluorenone (79) with an exceptionally low yield of 0.08% of the initial 78. Here, structural features determine the migration of the aroyl group to the meta-position with regard to the phenolic oxygen atom. For the eventual recombination, the meta-position of a phenoxy radical is extremely deactivated (Table III). 

Kirmse and Horner160 have shown that the quantum yield, in photolysis with monochromatic light, of C6H5COCHN2 is lowered considerably by the presence of additional double bonds in conjugation with the carbonyl groups and by para- and mecarbon atom of the diazo group. 

The conformation of the host is very different in the yellow 2 1 (host guest) benzene clathrate, 19-1/2 benzene. Structure 19 in benzene clathrate does not have approximate mirror symmetry. The aroyl groups have an asymmetric transoid arrangement and the torsion angles C(3)-C(2)-C(16)-C(17) and C(6)-C(7)-C(23)-C(24) are 155.24(12)° and 158.45(12)°,... 

The basic component is liberated upon fusion with sode-lime and at the same time the aroyl group yields a hydrocarbon. Use the experimental details described for carboxylic acids, Section 9.6.15, p. 1261 characterise the base by the preparation of a suitable derivative. 

Deprotonation of 2-alkyl-3-aroyl-l/7-2-benzothiopyranium salts by triethylamine generates an ylidic 2-thianaphthalene which is resonance stabilized by the 3-aroyl group. Behaving as an tf-qui nodi methane, a cycloaddition with unchanged thiopyranium salt follows and a complex benzothiopyran is formed via the sulfonium compound 304 (Scheme 48) <1996CC1659>. 

In all cases, the cyclic amino substituent in the major diastereoisomer is oriented cis to the aryl moiety of the participating aroyl group whereas the nonparticipating aroyl group is cis to the nitrile function. Whereas 2-naphthyl-substituted diones from oxetanes, 1,1 -naphthyl- and 1-(1-naphthyl)-2-phenyl ethanedione are unreactive. The latter effect probably reflects the nn nature of the lowest excited triplet state of these diones. 

In contrast to 83 and 85, 1,2-dimethyl-4,5-dihydroimidazole (89, n = 2) and 1,2-dimethyl- 1,4,5,6-tetrahydropyrimidine (89, n = 3) underwent direct acylation with two equivalents of aroyl chloride to give diacylenediamines 90 rather than enol benzoates. Their acid hydrolysis with sulfuric acid at water bath temperatures results in cleavage of one of the aroyl groups and benzoyl-substituted 1,1-enediamines 91 are formed in moderate yields (equation 31)103. 

Photolysis of 2-benzoyl-1,2-dihydroisoquinaldonitrile (8) with 2537 A light in acetonitrile or benzene solution, using a high-pressure mercury source, the yield of nitrile was lower. The photolyses also produced a low yield of the aldehydic fragment corresponding to the aroyl group. 

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