申请人:Wacker-Chemie GmbH
公开号:US05008392A1
公开(公告)日:1991-04-16
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.
该发明涉及一种利用新型马来酸酯作为起始原料制备吡啶-2,3-二羧酸酯的过程。在该过程中,首先将2,3-二卤马来酸酯与氨或铵盐在排除水的条件下,在至少50度的温度下反应,形成新型2-氨基-3-卤马来酸酯,然后在第二步中,将这些产物与α,β-不饱和醛或酮在存在酸性催化剂和酸中和剂的条件下,在至少50度的温度下反应,加热直到形成吡啶-2,3-二羧酸酯。这种类型的吡啶-2,3-二羧酸酯可以用作例如基于咪唑啉的除草剂合成的中间体。本发明还涉及新型的2-氨基-3-卤马来酸酯,可用于生产最终产品吡啶-2,3-二羧酸酯。