Process for the preparation of pyridine-2,3-dicarboxylic acid es

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

1989-11-27

1991-04-16

Ramsuer, Robert W.

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C07D213803

Patent

active

050083929

ABSTRACT:
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.

REFERENCES:
patent: 2724714 (1955-11-01), Jones
patent: 4723011 (1988-02-01), Doehner
patent: 4871859 (1989-10-01), Gupton et al.
patent: 4948896 (1990-08-01), Nagao
March, Advanced Organic Chemistry, 3rd edition, 1985, Wiley and Sons, pp. 364-365.

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