Crotonic acid, reaction with ammonia

Action of Hydrogen and of Ammonia.— Another reaction of aceto acetic ester should be mentioned. When hydrogen (sodium amalgam), ammonia or alkyl primary amines react with aceto acetic ester, crotonic acid (p. 173) CHs—CH = CH—COOH, or derivatives of it are obtained. The fact that crotonic acid contains a double bond seems to indicate the presence of a double bond in aceto acetic ester, and would be evidence for the enol form. 

From Enamines and Mercaptocarboxylic Acids. In the course of their wider study of the reaction between enamines and thiol adds, Klemmensen et have described a smooth condensation of enamines (312) derived from ethyl acetoacetate and ammonia or methylamine (/.e. ethyl j8-amino-crotonates) with a-mercaptocarboxylic acids (311) to thiazolidinones (313). The cyclization involves the addition of the thiol group, of (311), to the double bond, and amide formation between the amine and acid. ... 

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