Process for the preparation of pyridine-2,3-dicarboxylic acid esters
US5008392A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 27, 1989 |
| Grant date | Apr 16, 1991 |
| Priority date | — |
| Expiry date | Nov 27, 2009 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07D213/80
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.