Homocarboxylic anhydrides

We have already considered the use of mixed anhydrides and so in this section we shall be concerned with homocarboxylic anhydrides. The use of anhydrides constitutes the most frequently reported method after the use of an acyl chloride and aluminum chloride. Anhydrides from monocarboxylic acids yield ketones, and cyclic anhydrides derived from dicarboxylic acids afford keto acids. Very nucleophilic aromatic compounds react with trifluoroacetic anhydride in the absence of a catalyst. The confirmation of aromatic character invariably involves establishing reactivity towards a range of electrophiles. Trifluoroacetic anhydride reacts with homoazulene in the presence of an excess of triethylamine to afford 1-tri-fluoroacetylhomoazulene in 91-95% yield. The preparations of 3-aroylpropanoic acids from succinic anhydride and 4-aroylbutanoic acids from glutaric anhydride have been known for many years. Maleic anhydride can be used in a similar way to prepare 3-aroylacrylic acids. We will now concentrate our attention on more recent examples. 

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