| 摘要 |
Lower alkyl esters of 3-amino crotonates substituted by halogen in the C-4 position, e.g. ethyl 3-amino-4,4,4-trifluoro-crotonate, in which the amino group optionally may be substituted by one or two C1 to C3 alkyl groups or by one or two aryl groups, e.g. phenyl, are synthesized by thermolysis of ammonium salts of corresponding lower alkyl esters of acetoacetic acid substituted in the C-4 position by halogen, and removal of the resulting water of reaction. The water of reaction may be removed by an entraining agent, which preferably has a specific gravity heavier than that of the aqueous phase which forms in the reaction. This minimizes yield losses due to the ammonium salt becoming dissolved in the aqueous phase and results in especially high yields. Formation of the ammonium salt and thermolysis can be carried out simultaneously. Alternatively, it is possible to start from a molten ammonium salt of the halogencrotonate, e.g. the salt of the lower alkyl ester of 4,4,4-trifluoroacetoacetic acid, or to produce the salt in situ, and to pass an inert gas through the molten salt under thermolytic conditions and in the absence of a solvent. In this way the desired product can be produced in high yield and in high purity. This alternative can be implemented as a continuous process.
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