Acyl halides compounds

Acyl halides, both aliphatic and aromatic, react with the sodium derivative, but the product depends largely on the solvent used. Thus acetyl chloride reacts with the sodium derivative (E) suspended in ether to give mainly the C-derivative (t) and in pyridine solution to give chiefly the O-derivative (2). These isomeric compounds can be readily distinguished, because the C-derivative (1) can still by enolisation act as a weak acid and is therefore... 

The acylpalladium complex formed from acyl halides undergoes intramolecular alkene insertion. 2,5-Hexadienoyl chloride (894) is converted into phenol in its attempted Rosenmund reduction[759]. The reaction is explained by the oxidative addition, intramolecular alkene insertion to generate 895, and / -elimination. Chloroformate will be a useful compound for the preparation of a, /3-unsaturated esters if its oxidative addition and alkene insertion are possible. An intramolecular version is known, namely homoallylic chloroformates are converted into a-methylene-7-butyrolactones in moderate yields[760]. As another example, the homoallylic chloroformamide 896 is converted into the q-methylene- -butyrolactams 897 and 898[761]. An intermolecular version of alkene insertion into acyl chlorides is known only with bridgehead acid chlorides. Adamantanecarbonyl chloride (899) reacts with acrylonitrile to give the unsaturated ketone 900[762],... 

Appaiendy a molai equivalent of catalyst (AlCl ) combines with the acyl halide, giving a 1 1 addition compound, which then acts as the active acylating agent. Reaction with aromatics gives the AlCl complex of the product ketone hberating HX ... 

Addition to Carbonyl Compounds. Unlike Grignard and alkykitliium compounds, trialkylboranes are inert to carbonyl compounds. The air-catalyzed addition to formaldehyde is exceptional (373). Alkylborates are more reactive and can transfer alkyl groups to acyl halides. The reaction provides a highly chemoselective method for the synthesis of ketones (374). 

A very useful procedure for introducing a cyano group into a pyridazine ring is the Reissert-type reaction of the A/-oxide with cyanide ion in the presence of an acyl halide or dimethyl sulfate. The cyano group is introduced into the a-position with respect to the A-oxide function of the starting compound. The yields are, however, generally poor. In this way, 6-cyanopyridazines (111) can be obtained from the corresponding pyridazine 1-oxides (Scheme 33). 

FRIEDEL - CRAFTS Alkylation-Acylation Alkylation or acylation ol aromatic compounds by means of alryl halides, alcohols.alkenes, acyl halides in the presence of Lewis acids... 

Friedel-Crafts acylation usually involves the reaction of an acyl halide, a Lewis acid catalyst, and the aromatic substrate. Several species may function as the active electrophile, depending on the reactivity of the aromatic compound. For activated aromatics, the electrophile can be a discrete positively charged acylium ion or the complex formed... 

Acylation of various oxygen functions by use of common and commercially available fluonnated carboxylic acid denvatives such as trifluoroacetic anhydride or the corresponding acyl halides have already been discussed sufficiently in the first edition [10] Therefore only exceptional observations will be described in this section In the past 15 years, many denvatizations of various nonfluonnated oxygen compounds by fluoroacylation were made for analytical purposes. Thus Mosher s acid chlorides for example became ready-to-use reagents for the determination of the enantiomeric purity of alcohols and amines by NMR or gas-liquid chromatographic (GLC) techniques [//] (equation 1)... 

Codeposition of silver vapor with perfluoroalkyl iodides at -196 °C provides an alternative route to nonsolvated primary perfluoroalkylsilvers [272] Phosphine complexes of trifluaromethylsilver are formed from the reaction of trimethyl-phosphme, silver acetate, and bis(trifluoromethyl)cadmium glyme [755] The per-fluoroalkylsilver compounds react with halogens [270], carbon dioxide [274], allyl halides [270, 274], mineral acids and water [275], and nitrosyl chloride [276] to give the expected products Oxidation with dioxygen gives ketones [270] or acyl halides [270] Sulfur reacts via insertion of sulfur into the carbon-silver bond [270] (equation 188)... 

Although acyl fluorides, bromides, and iodides are all known classes of organic compounds, they are encountered far- less frequently than are acyl chlorides. Acyl chlorides will be the only acyl halides discussed in this chapter. 

The salts of the thiol react with alkyl and acyl halides to form alkyl or acyl derivatives (Table II). For a discussion of the constitution of these compounds see Section IV, D. 

Friedel-Crafts acylation reactions usually involve the interaction of an aromatic compound with an acyl halide or anhydride in the presence of a catalyst, to form a carbon-carbon bond [74, 75]. As the product of an acylation reaction is less reactive than its starting material, monoacylation usually occurs. The catalyst in the reaction is not a true catalyst, as it is often (but not always) required in stoichiometric quantities. For Friedel-Crafts acylation reactions in chloroaluminate(III) ionic liquids or molten salts, the ketone product of an acylation reaction forms a strong complex with the ionic liquid, and separation of the product from the ionic liquid can be extremely difficult. The products are usually isolated by quenching the ionic liquid in water. Current research is moving towards finding genuine catalysts for this reaction, some of which are described in this section. 

The A-(l-acyloxyalkyl)amides or carbamates arc easily prepared from the corresponding hydroxy compounds by conventional acylation methods, such as heating with the required carboxylic acid in the presence of a strong acid or treatment with acyl halides or acid anhydrides1. 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

The scope of this reaction is similar to that of 10-21. Though anhydrides are somewhat less reactive than acyl halides, they are often used to prepare carboxylic esters. Acids, Lewis acids, and bases are often used as catalysts—most often, pyridine. Catalysis by pyridine is of the nucleophilic type (see 10-9). 4-(A,A-Dimethylamino)pyridine is a better catalyst than pyridine and can be used in cases where pyridine fails. " Nonbasic catalysts are cobalt(II) chloride " and TaCls—Si02. " Formic anhydride is not a stable compound but esters of formic acid can be prepared by treating alcohols " or phenols " with acetic-formic anhydride. Cyclic anhydrides give monoesterified dicarboxylic acids, for example,... 

Unsymmetrical as well as symmetrical anhydrides are often prepared by the treatment of an acyl halide with a carboxylic acid salt. The compound C0CI2 has been used as a catalyst. If a metallic salt is used, Na , K , or Ag are the most common cations, but more often pyridine or another tertiary amine is added to the free acid and the salt thus formed is treated with the acyl halide. Mixed formic anhydrides are prepared from sodium formate and an aryl halide, by use of a solid-phase copolymer of pyridine-l-oxide. Symmetrical anhydrides can be prepared by reaction of the acyl halide with aqueous NaOH or NaHCOa under phase-transfer conditions, or with sodium bicarbonate with ultrasound. 

These reactions are most important for the preparation of acyl fluorides. " Acyl chlorides and anhydrides can be converted to acyl fluorides by treatment with polyhydrogen fluoride-pyridine solution" or with liquid HF at — 10°C. Formyl fluoride, which is a stable compound, was prepared by the latter procedure from the mixed anhydride of formic and acetic acids. Acyl fluorides can also be obtained by reaction of acyl chlorides with KF in acetic acid or with DAST. Carboxylic esters and anhydrides can be converted to acyl halides other than fluorides by the inorganic acid halides mentioned in 10-77, as well as with PhsPXa (X = Cl or but this is seldom done. Halide exchange can be carried out in a... 

Reissert compounds (116) are prepared from the acyl halide by treatment with quinoline and cyanide ion. Treatment of 116 with sulfuric acid gives the... 

The Conversion of Acyl Halides to Ketones With Organometallic Compounds ... 

Similar additions have been successfully carried out with carboxylic acids, anhydrides, acyl halides, carboxylic esters, nitriles, and other types of compounds. These reactions are not successful when the alkene contains electron-withdrawing groups such as halo or carbonyl groups. A free-radical initiator is required, usually peroxides or UV light. The mechanism is illustrated for aldehydes but is similar for the other compounds ... 

---