Acetyl chloride, acylation with

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... 

Acetyl chloride reacts with (C5H5)Fe(CO)2 to produce an acyl derivative. 

TV-Acylation of (73) can be achieved with acyl chlorides and pyridine or triethylamine, or with ketene (75S547 p. 560). 7V-Trimethylsilylazetidin-2-ones have been reported to undergo acyldesilylation on treatment with acetyl chloride. Acylation of (73) with imidates (78) at 150-160 °C was followed by ring expansion to give the pyrimidin-4-ones (79). Pyrimid-4-ones were obtained from a similar reaction of imidates with 4-alkoxyazetidin-2-ones (74CB270). Acylation with subsequent ring expansion also occurs with dithioimidates (73CPB1305). 

Preparation of ethylthio-138 and phenylthio-carbene complexes139 was similarly achieved by treatment of the corresponding isolated tetrabutylammonium acylate complexes in CH2C12 at 40 °C with acetyl chloride, then with the corresponding thiols at 0 °C as illustrated in equation 64 for the phenylthio derivatives. 

The C-acyl derivatives constitute the regular products. Thus, acylation of 5,5-dimethyl-3-(l-pyrrolidyl)-2-cyclohexen-l-one with acetyl chloride or with chlorides of aromatic acids affords 2-acyl derivatives.248" On the other hand, an analogous reaction with... 

Acid derivatives differ greatly in their reactivity toward nucleophilic acyl substitution. For example, acetyl chloride reacts with water in a violently exothermic reaction, while acetamide is stable in boiling water. Acetamide is hydrolyzed only by boiling it in strong acid or base for several hours. 

Acyl halides such as acetyl chloride react with water to regenerate the starting acid and they react with alcohols to yield esters. The reaction is often facilitated by the presence of a tertiary amine catalyst. Although this may function purely as a base to neutralize the hydrochloric acid which is formed in the reaction, bases such as dimethylaminopyridine can also activate the carboxyl group via the formation of the intermediate shown in Scheme 3.66. 

Scheme 9.127. A representation of a pathway for the formation of N-ethyl ethanoamide (N-ethylacetamide, CH3CONHCH2CH3) from the reaction of ethanoyl chloride (acetyl chloride, CH3COCI) with ethylamine (ethanamine, aminoethane, CH3CH2NH2).The chlorine on the acyl function has been replaced by a nitrogen.

TTie true ketones, in which the >CO group is in the side chain, the most common examples being acetophenone or methyl phenyl ketone, C HjCOCH, and benzophenone or diphenyl ketone, C HjCOC(Hj. These ketones are usually prepared by a modification of the Friedel-Crafts reaction, an aromatic hydrocarbon being treated with an acyl chloride (either aliphatic or aromatic) in the presence of aluminium chloride. Thus benzene reacts with acetyl chloride... 

Direct nitration of aniline and other arylamines fails because oxidation leads to the formation of dark colored tars As a solution to this problem it is standaid practice to first protect the ammo group by acylation with either acetyl chloride or acetic anhydride... 

Even saturated hydrocarbons give ketones with acyl chlorides (20). For example, cyclohexane and acetyl chloride react in the presence of aluminum chloride to give l-acetyl-2-methylcyclopentane. 

Sulfonated styrene—divinylbensene cross-linked polymers have been appHed in many of the previously mentioned reactions and also in the acylation of thiophene with acetic anhydride and acetyl chloride (209). Resins of this type (Dowex 50, Amherljte IR-112, and Permutit Q) are particularly effective catalysts in the alkylation of phenols with olefins (such as propylene, isobutylene, diisobutylene), alkyl haUdes, and alcohols (210) (see Ion exchange). Superacids. 

Acylation. Aliphatic amine oxides react with acylating agents such as acetic anhydride and acetyl chloride to form either A[,A/-diaLkylamides and aldehyde (34), the Polonovski reaction, or an ester, depending upon the polarity of the solvent used (35,36). Along with a polar mechanism (37), a metal-complex-induced mechanism involving a free-radical intermediate has been proposed. 

Acylation. Reaction conditions employed to acylate an aminophenol (using acetic anhydride in alkaU or pyridine, acetyl chloride and pyridine in toluene, or ketene in ethanol) usually lead to involvement of the amino function. If an excess of reagent is used, however, especially with 2-aminophenol, 0,A/-diacylated products are formed. Aminophenol carboxylates (0-acylated aminophenols) normally are prepared by the reduction of the corresponding nitrophenyl carboxylates, which is of particular importance with the 4-aminophenol derivatives. A migration of the acyl group from the O to the N position is known to occur for some 2- and 4-aminophenol acylated products. Whereas ethyl 4-aminophenyl carbonate is relatively stable in dilute acid, the 2-derivative has been shown to rearrange slowly to give ethyl 2-hydroxyphenyl carbamate [35580-89-3] (26). 

Friedel-Crafts Acylation. The Friedel-Crafts acylation procedure is the most important method for preparing aromatic ketones and thein derivatives. Acetyl chloride (acetic anhydride) reacts with benzene ia the presence of aluminum chloride or acid catalysts to produce acetophenone [98-86-2], CgHgO (1-phenylethanone). Benzene can also be condensed with dicarboxyHc acid anhydrides to yield benzoyl derivatives of carboxyHc acids. These benzoyl derivatives are often used for constmcting polycycHc molecules (Haworth reaction). For example, benzene reacts with succinic anhydride ia the presence of aluminum chloride to produce P-benzoylpropionic acid [2051-95-8] which is converted iato a-tetralone [529-34-0] (30). 

With Acyl Halides, Hydrogen Halides, and Metallic Halides. Ethylene oxide reacts with acetyl chloride at slightly elevated temperatures in the presence of hydrogen chloride to give the acetate of ethylene chlorohydrin (70). Hydrogen haUdes react to form the corresponding halohydrins (71). Aqueous solutions of ethylene oxide and a metallic haUde can result in the precipitation of the metal hydroxide (72,73). The haUdes of aluminum, chromium, iron, thorium, and zinc in dilute solution react with ethylene oxide to form sols or gels of the metal oxide hydrates and ethylene halohydrin (74). 

Acylation of pyridazinethiones with acetyl chloride or benzoyl chloride gives the corresponding S-acylated products. 6-Mercaptopyridazine-3(2//)-thione gives either mono- or di-S-acylated products. A bispyridazinyl derivative is formed when phosgene or thiophos-gene is used as acylating agent. 

Triazoles are acylated with acyl halides, usually initially at the 1-position, but the acyl group may migrate to the 2-position on heating or on treatment with base. Thus acetylation with acetyl chloride often gives 1-acetyl derivatives, which rearrange to the 2-isomers above 120 °C (74AHCil6)33). 

Acylations were often carried out with diaziridines. Twofold acylation is normally observed when two NH groups are present. Most acylations were performed with benzoyl chloride, acetyl chloride or phenyl isocyanate (B-67MI50800). Ring opening reactions during acylation, foreseeable for intermediates of electrophilic attack on nitrogen, were observed only seldom, provided mild conditions were used. 

The formation of acyl halide-Lewis acid complexes have been observed by several methods. For example, both 1 1 and 1 2 complexes of acetyl chloride, with AICI3 can be observed by NMR spectroscopy. The existence of acylium ions has been demonstrated by X-ray diffraction studies on crystalline salts. For example, crystal structure determinations have been reported for /i-methylphenylacylium and acetylium ions as SbFg salts. There is also a good deal of evidence from NMR measurements which demonstrates that acylium ions can exist in nonnucleophilic solvents. " The positive charge on acylium ions is delocalized onto the oxygen atom. This delocalization is demonstrated in particular by the short O—C bond lengths in acylium ions, which imply a major contribution from the structure having a triple bond ... 

The strong para-directing influence of fluorine in Fnedel-Crafts acylation is illustrated by the reaction of fluorotoluenes with acetyl chloride Treatment of 2-fluorotoluene, 3-fluorotoluene, and 2-fluoro-3-methyltoluene with acetyl chloride and aluminum chloride gives, respectively, 91, 82, and 80% substitution para to fluorine [27]... 

Bis(tnfluoromethyl)-4,5-dihydrooxazin-6-ones [28] and their O-acetylated dcnvatives [96] are formed on treatment of acyl imines with acetyl chloride-hiethylamine at room temperature. The reaction was interpreted as a cycloaddition reaction involving a ketene [28] However, the periselectivity and regiochemistry of this reactwn-are not in agreement with results obtained from the reaction of... 

Friedel-Crafts acylation of the individual isomers of xylene with acetyl chloride and aluminum chloride yields a single product, different for each xylene isomer, in high yield in each case. Write the structures of the products of acetylation of o-, m-, and p-xylene. 

Partial rate factors may be used to estimate product distributions in disubstituted benzene derivatives. The reactivity of a particular position in o-bromotoluene, for example, is given by the product of the partial rate factors for the corresponding position in toluene and bromobenzene. On the basis of the partial rate factor data given here for Friedel-Crafts acylation, predict the major product of the reaction of o-bromotoluene with acetyl chloride and aluminum chloride. 

The reaction of the enamine (96) with acetyl chloride was reported (72) to afford no acyl derivative but the aminocyclobutanone (97) and the hydrochloride of the enamine. 

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