2-amino-3-halomaleic acid esters

Details 2-amino-3-halomaleic acid esters 2-amino-3-halomaleic acid esters

1990-12-21

1992-03-31

Shippen, Michael L.

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

Organic compounds

Carboxylic acid esters

C07C22900

Patent

active

051010674

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.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.

REFERENCES:
patent: 4670466 (1987-02-01), Chaiet
Wanner, J. Med. Chem., 23, pp. 85-87 (1980).
Burger, "Medical Chemistry", 2nd Ed., pp. 72-88 (1960).
Liebigs Ann. Chem., pp. 1658-1664, Bonse et al., 1981.
European Search Report of Eur. Pat. App. 89-122075 (1991).

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