Aroyl halides

Various organotin reagents react with acyl and aroyl halides under mild conditions without decarbonylation to give carbonyl compounds[390,39l]. Alkyl- or alkenyltin reagents react with acyl and aroyl chlorides to give ketones[548.733,734]. One example is the preparation of the a,/3-dnsaturated 7-keto esters 860 and 861, carried out under a CO atmosphere[735]. The reaction has been applied intramolecularly to the synthesis of the macrocyclic keto... 

There are alternatives to the addition-elimination mechanism for nucleophilic substitution of acyl chlorides. Certain acyl chlorides are known to react with alcohols by a dissociative mechanism in which acylium ions are intermediates. This mechanism is observed with aroyl halides having electron-releasing substituents. Other acyl halides show reactivity indicative of mixed or borderline mechanisms. The existence of the SnI-like dissociative mechanism reflects the relative stability of acylium ions. 

Thallium(I) Compounds. Carboxylic anhydrides can be prepared by the reaction of acyl or aroyl halides in ether with thallium(I) carboxylates (26) ... 

Solid Catalysts. Nafion-H is an active catalyst for acylation with aroyl halides and anhydrides.60,61 The reaction is carried out at the boiling point of the aromatic hydrocarbons. Yields with benzoyl chloride using 10-30% Nafion-H for benzene, toluene, and p-xylene are 14%, 85% and 82%, respectively. Attempted acylation with acetyl chloride, however, led to HC1 evolution and ketene formation. Nation resin-silica nanocomposite materials containing a dispersed form of the resin within silica exhibits significantly enhanced activity in Friedel-Crafts acylations.62,63... 

Extensive studies of the mechanism of formation of dialkylhydrazido(2—) complexes from [Mo(N2)2(dppe)2] (M = Mo, W) have revealed a free radial mechanism for addition of the first alkyl group with loss of one N2 molecule as the rate-determining step.484 Addition of the second alkyl group proceeds via an SN 2 mechanism (see Scheme 6) and the effect of the metal and coligands on reaction rates has been studied in detail.485 Acoyl and aroyl hydrazido(2 —) complexes can be obtained by reaction of the N2 complexes with acoyl or aroyl halides in the presence of acid (equation 177).486... 

Isosorbide 2-acetate may also be prepared by transesterification of equimolar amounts of isosorbide 2,5-diacetate and isosorbide in the presence of acidic or basic catalysts (KOH or p-toluenesulfonic acid, for 1 hat 140°, and distillation104,107 of the 2-acetate at 100° at 27 kPa 89%). Subsequent esterification of the resulting isosorbide mononitrates with acyl and aroyl halides... 

When 1,6-naphthyridine is reacted with potassium cyanide and with an acyl or aroyl halide, the 5,6-addition product (92) is obtained in poor yields... 

The reported gas-phase acylations with Nafion-H catalyst were generally carried out at the boiling point of the hydrocarbon to be acylated. The yield of aroylation reaction depends on the relative amount of the catalyst used. Optimum yields were obtained when 10-30% of Nafion-H was employed relative to the aroyl halide. Although this procedure allows very clean reactions with no complex formation and easy work-up procedures, it is presently limited to only aroylation. Attempted acetylation of aromatics with acetyl chloride under similar conditions led to thermal HC1 elimination from the latter to form ketene and products thereof. In the reaction of acetyl chloride by itself with Nafion-H, diketene was detected by IR and NMR... 

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. 

Kinetic studies on the reaction between trans- M(l Mdppe)2 (M = Mo) with alkyl, acyl, or aroyl halides, in the dark, show that the rate of the reaction is independent of the concentration and nature of the alkyl halide, but has a first-order dependence on the concentration of the complex ( bs = 1.3 0.2 x 10 4 sec ). The tungsten reaction requires light. 

Treatment of the magnesium enolate of diethyl malonate with an aroyl halide, followed by decarboxylation... 

Reductive coupling of ArCOCl.3 Aroyl halides substituted by an electron-withdrawing group couple to biphenyls when heated with a disilane such as 1 at 160° in the presence of a Pd catalyst. 

The original reaction procedures have steadily been extended and improved, and an overwhelming number of catalyst systems are now known. Besides aryl halides, many additional substrates, for example aryl triflates, diazonium salts, sulfonyl and aroyl halides, carboxylic and phosphonic acids, and even arenes have been used as... 

Supported heterogeneous Pd catalysts catalyze the decarbonylation of aroyl halides at temperature higher than 300 °C (equation 163)1074,1075. EuC13 is also an interesting decarbonylation catalyst (equation 164). 

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