Imidazole derivatives intramolecular catalysis

Because esters 745 a, b of imidazole-acetic acid are unstable when stored for long periods, owing to intramolecular catalysis by the imidazole moiety, the esters should be converted into their salts or free acids and stored as such. Only tert-butyl imidazole-(4,5)acetates derived from tert-butyl 4-chloroacetoacetate seem to be stable [232, 233]. N-alkyl-substituted amidines give rise to a mixture of alkyl N-alkylimidazole-4- and 5-acetates [232, 233]. 

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