Process for the preparation of pyridine-2, 3-dicarboxylic...

Details Process for the preparation of pyridine-2, 3-dicarboxylic... Process for the preparation of pyridine-2, 3-dicarboxylic...

C - Chemistry, Metallurgy

07

C

260/296, 260/297

C07C 229/30 (2006.01) C07D 213/80 (2006.01) C07D 213/803 (2006.01)

Patent

CA 2004012

PROCESS FOR PREPARATION OF PYRIDINE-2, 3-DICARBOXYLIC ACID ESTERS AND NOVEL 2-AMINO-3 HALOMALEIC ACID ESTERS ABSTRACT OF THE DISCLOSURE 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°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°C with heat being supplied until the pyridine-2,3-dicarboxylic acid esters have been formed. Pyridine-2,3-dicar- boxylic acid esters of this type can be used, for example, as intermediates for synthesis of herbicides based on imidazoline. The present invention also relatesto novel 2-amino-3-halomaleic acid esters, which are useful for producing the final product pyridine-2,3-dicarboxylic acid esters.

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