Aliphatic Acid Anhydrides

As mentioned in the Introduction (p 5), chlorosulfonic acid reacts easily with carboxylic acid anhydrides giving excellent yields of the corresponding alkanoyl chlorides, which provides a useful synthetic route to these compounds. For example, butanoic anhydride 134 by treatment with chlorosulfonic acid (0.8 equivalents) at —5 °C, followed by vacuum distillation, afforded butanoyl chloride 135 (95% yield) (Equation 54).  

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The choice of type of derivative should be based on whether the chloride or anhydride is aliphatic or aromatic, because this factoi largely determines the reactivity. Aliphatic acid chlorides are best converted into their anilides, as in 4 above aromatic acid chloride may be similarly converted into their anilides, or they may be converted into their amides by shaking with an excess of ammonia (p, 120). (M.ps., pp. 544-545.) Aliphatic acid anhydrides should be converted into their crystalline anilides, but aromatic acid anhydrides arc best hydrolysed to the acid, which can then be converted into one of the standard derivatives (p. 349). 

The use of aliphatic acid anhydrides in place of acid chlorides offers many advantages these include ... 

Perkin condensation is the reaction between aromatic aldehydes and aliphatic acid anhydrides (in the presence of the sodium salt) to form p-arylacrylic acid... 

The conversion of c>-hydroxyaryl ketones la to chromones 2a and/or coumarins 3a with aliphatic acid anhydrides in the presence of the sodium or potassium salt of the corresponding acid and the reaction between lb and aromatic acid anhydrides and the salt of the corresponding acid to form flavones 2b (Allan-Robinson) is called the Kostanecki-Robinson (K-R) reaction. ... 

Cyclization of cyanohydrins with aliphatic acid anhydrides in the presence of strong acids (pAT < 1) or aromatic acids halides in the presence of SnCl4. 

Liquid crystal polyesters are made by a different route. Because they are phenolic esters, they cannot be made by direct ester exchange between a diphenol and a lower dialkyl ester due to unfavorable reactivities. The usual method is the so-called reverse ester exchange or acidolysis reaction (96) where the phenolic hydroxyl groups are acylated with a lower aliphatic acid anhydride, eg, acetic or propionic anhydride, and the acetate or propionate ester is heated with an aromatic dicarboxylic acid, sometimes in the presence of a catalyst. The phenolic polyester forms readily as the volatile lower acid distills from the reaction mixture. Many liquid crystal polymers are derived formally from hydroxyacids (97,98) and their acetates readily undeigo self-condensation in the melt, stoichiometric balance being automatically obtained. 

Another type of elimination reaction favoured under plasma conditions is the decarboxylation. Carbocyclic acids easily lose carbon dioxide to form the parent hydrocarbons. In acid anhydrides decarboxylation is followed by a decar-bonylation. Cyclic or bicyclic anhydrides fragment forming unsaturated compounds, a reaction which has been studied with phthalie anhydride 24>. This anhydride decomposes to dehydrobenzene which, in the absence of other compounds, dimerizes, trimerizes or polymerizes. Orientation experiments indicated similar results for aliphatic acid anhydrides. 

The substituted thieno[2,3-6]thienophene (262) in a mixture of an aliphatic acid anhydride and HC104 gave thieno[2, 3 5,4]thieno[2,3-c]pyrylium perchlorates (263), which with an excess of ammonia are converted into the corresponding thieno[2, 3 5,4]thieno[2,3-c]pyridines (264) (Scheme 17) <83KGS37>. 

The rearrangement of l-aryl-5-aminotetrazoles by the action of acetic anhydride to 2-arylamino-5-methyl-l,3,4-oxadiazoles or to their acetyl derivatives has been known for some time.101,102 This reaction may be widely generalized. The action of aromatic and aliphatic acid anhydrides and acid chlorides on 5-alkyl(aryl)tetrazoles produces 1,3,4-oxadiazoles in excellent yield. iV-Acyl tetr azoles (31) are formed as intermediates. These are converted with elimination of... 

Classically, this separation of roles was accomplished by utilizing substrates that differed drastically in their ability to form enolate anions. In fact, the various name reactions mentioned above are distinguished not by basic differences in mechanism, but by the nature of the components preferentially utilized as substrates. For example, in the Perkin reaction, the condensation of an aromatic aldehyde with an aliphatic acid anhydride is based on the fact that the electrophilic component, e.g. benzaldehyde, lacks a-hydrogens and therefore is incapable of forming an enolate. At the same time the utilized electrophile, acetic anhydride, contains a carbonyl group with reduced propensity to interact with nucleophiles. Hence, it is incapable of undergoing self-condensa-... 

Another way to form a-aminoketones from a-amino acids is via the Dakin-West reaction, in which amino acids are treated with aliphatic acid anhydrides to give ketone amides. Thus, reaction of ( )-phenylalanine with the appropriate aliphatic acid anhydrides followed by acidic hydrolysis afforded keto-amide 1271. Cyclization of 1272 with potassium cyanate gave 5-alkyl-4-benzyl-l,3-dihydroimidazol-2-ones 1273 (Scheme 322) <2002JHC375>. 

Aliphatic add chloride Aromatjc acid chloride Aliphatic acid anhydride Aliphatic ester Aromatic ester... 

Kostanecki acylation. Formation of chro-mones or coumarines by acylation of o-hydroxyaryl ketones with aliphatic acid anhydrides followed by cyclization. 

Graft copolymers were also produced by bubbling alkylene oxides through starch solutions in dimethyl sulfoxide in the presence of potassium naphthenate.2888,2889 Another approach involved grafting polyethylene oxide) to starch. Polyethylene oxide) was converted into a chloroformate derivative and subjected to a reaction with starch alkoxide 2890 Poly(alkylene glycol) could be grafted onto starch by means of cyclic aliphatic acid anhydride in the presence of 4-toluenesulfonic acid 2891 The products were water soluble. 

Acylation of thienothiophene derivatives 32 and 33 in an aliphatic acid anhydride - 70% perchloric acid system gives the corresponding pyrylium salts 36 (for compounds 32, = Me). 

Acylation of 3-acetonyl-5-alkylthieno[2,3-fe]thiophenes 208 and 3-acetonyl-5-methylthieno[3,2-fe]thiophenes (209) in a mixture of aliphatic acid anhydride and perchloric acid (actually, acylium perchlorate) was demonstrated (79KGS1424) to occur at the free a position followed by cyclization and formation of perchlorates of tricyclic pyrylium salts 210 and 211 (yields > 80%). The latter are transformed into thieno[2, 3 5,4]- (212) and -[2, 3 4,5]thieno[2,3-c]pyridmes 213 in yields higher than 90% by passing ammonia through their suspensions. 

Electroreduction of styrenes or alkyl methacrylates in the presence of aliphatic acid anhydrides or N-acylimidazoles with zinc anode brought about novel one-pot vicinal double C-acylation to afford the corresponding 1,4-diketones in good to high yields. This is an example of cross-coupling reaction with no use of halogenated compounds. 

A comparative study has been conducted into the thermal and thermooxidative degradation of PET and PBT polymer films and their model compounds, ethylene dibenzoate and butylene dibenzoate, in an oxygen atmosphere at 160 °C 832485. On the basis of the compounds identified by GC-MS, a mechanism was proposed for the degradation of the model compounds that involves oxidation at the a-methylene carbon with the formation of unstable peroxides and carboxylic acids a.l53. From the studies performed under N2 at 160 °C, it was concluded that benzoic acid and esters are products of the thermal degradation as illustrated in Schemes 15 and 16, while benzoic and aliphatic acids, anhydride and alcohols were due to thermooxidative degradation. 

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