Dicarboxylic acid hydrazides anhydrides

The usual range of carboxylic acid derivatives can be prepared and interconverted. Both carboxylic acid and ester functions are capable of reduction by lithium aluminum hydride to alcohols, or by controlled potential reduction to aldehydes. Attempts to form the anhydride from imidazole-4,5-dicarboxylic acid by heating with acetic anhydride failed. Instead, compound (199) is formed. This product forms the monoester (200) when heated with methanol and the hydrazide (201) when treated similarly with hydrazine (Scheme 107) (75S162). The corresponding l-methyl-4,5-dicarboxylic acid loses the 4-carboxyl group when heated with acetic anhydride, but in boiling aniline it is transformed into the 1-methyl-4-carboxanilide (79H(12)186). 

Usually decarboxylation is accomplished by heating the acids above their melting points, often in the presence of a copper-chromium catalyst. Imidazole-4,5-dicarboxylic acid can be monodecarboxylated by heating its monoanilide imidazole- and benzimidazole-2-carboxylic acids decarboxylate very readily indeed, so readily that the carboxyl function makes a useful blocking group in metallation procedures (see Scheme 7.2.1) [3-5]. A potentially useful method of preparation of imidazole-4-carboxylic acid derivatives heats the 4,5-dicarboxylic acid (2) with acetic anhydride to form (1), which is essentially an azolide and very prone to nucleophilic attack which cleaves the nitrogen-carbonyl bond (Scheme 8.3.1). With methanol the methyl ester (3) is formed with hydrazines the 4-hydrazides (4) result [6]. 

Hydrazides (s. a. Carboxylic acid hydrazides) reduction with borane 26,56 Hydrazine (s. a. Wolff-Kishner reduction) 26,15 reaction with dicarboxylic acid anhydrides 8, 482... 

Oxindolylmethyl) pyridine-3,5-dicarboxylic acid 5-methyl ester refluxed 1 min. in acetic anhydride enollactone (Y 94%) added below 5° to a mixture of hydrazine hydrate and methanol, shaken until dissolved hydrazide (Y 90%). F. e. s. H. Plieninger, M. Schach von Wittenau, and B. Kiefer, B. 91, 2095 (1958). 

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