Wacker-chemie Gmbh

Josef Meier

Wolfgang Deinhammer

Konrad Krageloh

The invention relates to a process for the preparation of .beta.-ketocarboxylic acid esters of the general formula ##STR1## in which R.sup.1 is an alkyl radical having 1 to 4 C atoms, R.sup.2 is an alkyl radical or alkenyl radical having 2 to 15 C atoms or a phenyl radical and R.sup.3 is hydrogen or an alkyl or alkenyl radical having 1 to 6 C atoms, characterized in that acetocarboxylic acid esters of the general formula ##STR2## in which R.sup.1 and R.sup.3 are as defined, are reacted with calcium hydroxide or calcium oxide in the presence of an organic solvent and in the absence of water, the calcium chelate complexes formed are acylated with carboxylic acid chloride and the products are then cleaved with aqueous ammonium salt solution to form the .beta.-ketocarboxylic acid esters of formula (I). The .beta.-ketocarboxylic acid esters readily accessible by the process according to the invention can be used as important intermediates in the synthesis of pharmaceutically active ingredients or plant protection agents.

Process for the preparation of .beta.-ketocarboxylic acid esters

The invention relates to a process for the preparation of pyridine-2,3-dicarboxylic acid esters using novel maleic acid esters as starting materials. In the process, in a first process step, 2,3-dihalomaleic acid esters are reacted with ammonia, or ammonium salts, with the exclusion of water at a temperature of at least 50.degree.0 C. to form novel 2-amino-3-halomaleic acid esters, and these are subsequently reacted further in a second process step with .alpha.,.beta.-unsaturated aldehydes, or ketones, in the presence of an acidic catalyst and acid-binding agents at a temperature of at least 50.degree. C. with heat being supplied until the pyridine-2,3-dicarboxylic acid esters have been formed. Pyridine-2,3-dicarboxylic acid esters of this type can be used for example, as intermediates for synthesis of herbicides based on imidazoline. The present invention also relates to novel 2-amino-3-halomaleic acid esters, which are useful for producing the final product pyyridine-2,3-dicarboxylic acid esters.

2-amino-3-halomaleic acid esters

The invention relates to a process for the preparation of pyridine-2,3-dicarboxylic acid esters using novel maleic acid esters as starting materials. In the process, in a first process step, 2,3-dihalomaleic acid esters are reacted with ammonia, or ammonium salts, with the exclusion of water at a temperature of at least 50.degree. C. to form novel 2-amino-3-halomaleic acid esters, and these are subsequently reacted further in a second process step with .alpha.,.beta.-unsaturated aldehydes, or ketones, in the presence of an acidic catalyst and acid-binding agents at a temperature of at least 50.degree. C. with heat being supplied until the pyridine-2,3-dicarboxylic acid esters have been formed. Pyridine-2,3-dicarboxylic acid esters of this type can be used, for example, as intermediates for synthesis of herbicides based on imidazoline. The present invention also relates to novel 2-amino-3-halomaleic acid esters, which are useful for producing the final product pyridine-2,3-dicarboxylic acid esters.

Growing community of inventors

Burghausen, Germany

Josef Meier