Dicarboxylic acid acyl halides

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,... 

Heating dicarboxylic acids, HOOC(CH,) COOH n = 2 or 3), forms cyclic anhydrides by intramolecular dehydration [Problem 16.22(a), (6)]. Anhydrides resemble acid halides in their reactions. Because acetic anhydride reacts less violently, it is often used in place of acetyl chloride. Acid anhydrides can also be used to acylate aromatic rings in electrophilic substitutions. 

This is a general method of preparing enamines from a secondary aliphatic amine and cyclohexanone or cyclopentanone. Acylation of such enamines is the first step in a general procedure for increasing the chain length of a carboxylic acid by 5 or 6 carbon atoms and of a dicarboxylic acid by 10 or 12 carbon atoms.6 Alkylation of enamines of cyclohexanones by alkyl halides 7 or electrophilic olefins,8 followed by hydrolysis, is a good route to a-monoalkyl cyclohexanones. 

An important reaction for synthesis of alkyl and dialkylethanoic acids (RX and R X are primary or secondary alkyl halides) dicarboxylic acids (RX = haloester) unsaturated acids (RX = an unsaturated halide, best for allylic halides) /3-keto acids (R = acyl chloride) (see Sections 18-8C and 18-8D). 

Monocationic acyl ions are readily prepared as persistent species in solutions of low nucleophile strength.68 These acyl ions have been thoroughly characterized by IR and NMR spectroscopy, and several acyl ion salts have been characterized by X-ray crystallography. The monocationic acyl ions are often prepared in situ from carboxylic acids, esters, or anhydrides, by the action of a strong Brpnsted acid, or the ions can be prepared from ionization of an appropriate acid halide with a strong Lewis acid. Both methods have been used to prepare acyl-centered dications, some of which can be considered distonic superelectrophiles. As described previously, dicarboxylic acids cleave to the bis-acyl ions in superacid (FSChH-SbFs) provided that the acyl cations are separated by at least three methylene units (eq 54).55 The first bis-acyl dications were reported by Olah and Comisarow, being prepared by the reactions of dicarboxylic acid fluorides with superacidic SbFs (eq 72).69... 

Note Such acyl halides are only seldom characterized and rarely even isolated. l,8-Naphthyridine-2,7-dicarboxylic acid gave l,8-naphthyridine-2,7-dicarbonyl chloride (12, R = H) (SOCl2, reflux 57%) 1133 4-octyloxy-l,8-naphthyridine-2,7-dicarbonyl chloride (12, R = OCgH17) was made similarly but not characterized.1376... 

The alkylaluminum halide-induced Friedel-Crafts acylation is a very general and synthetically useful reaction that allows the functionalization of unsaturated fatty compounds. Acylations were carried out with different acylating agents such as acyl chlorides, dicarboxylic acid dichlorides, cyclic anhydrides, unsaturated acyl chlorides, and aromatic and heteroaromatic carboxylic acid chlorides, yielding a large... 

Chapter 16 (Section 16.6) introduced dicarboxylic acids along with their common and lUPAC names. The common names and the lUPAC names are shown again in Table 20.1 for dicarboxylic acids of C2-C10. This chapter deals with the chemistry of carboxylic acids and their derivatives, and dicarboxylic acids have their acyl halide, ester, anhydride, and amide derivatives. The two carboxylic acid units lead to some interesting structural variations, however. 

In Summary The hydroxy group in COOH can be replaced by halogen by using the same reagents used to convert alcohols into haloalkanes—SOCI2 and PBrs. The resulting acyl halides are sufficiently reactive to be attacked by carboxylic acids to generate carboxyUc anhydrides. Cyclic anhydrides may be made from dicarboxylic acids by thermal dehydration. 

Acylation of pentafluorobenzene to form ketones either with acid halides or with anhydrides has been achieved with an excess of SbFs In the case of dicarboxylic acid dichlorides or anhydrides... 

A long-chain dicarboxylic acid may also form a cyclic acid anhydride, in which the -CO.O.CO- group forms part of a ring. Acid anhydrides can be prepared by reaction of an acyl halide with the sodium salt of a carboxylic acid, e.g. ... 

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