Process for making 2,6-difluoro pyridine
AssigneeThe Dow Chemical Company
InventorTerry G. Muench
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Abstract
It has been found that practical rates of formation of 2,6-difluoropyridine from 2,6-dichloropyridine and KF can be attained without resort to catalysts, high temperatures or large excesses of KF, if: A. dimethyl sulfoxide (DMSO) is employed as the reaction medium, B. the reaction mixture contains less than 0.015 grams of HF and 0.5 grams of K.sub.2 CO.sub.3 or KHCO.sub.3 per 100 grams of KF and less than 0.5 grams of water per 100 grams of DMSO, c. the difluoropyridine is distilled out as formed, and D. the reaction mixture is intensely stirred and kept at a temperature of 175.degree.-192.degree. C.
Claims10
In the process of preparing 2,6-difluoropyridine by reacting KF with an alpha-chloropyridine which is 2,6-dichloro- or 2-chloro-6-fluoropyridine, in dimethyl sulfoxide (DMSO) at an elevated temperature, essentially in the absence of initiators or catalysts, and distilling out the difluoropyridine as formed,
- the improvement whereby distilled difluoropyridine yields of at least 90% can be attained in reaction periods of 15 hours or less, without employing large excesses of KF or temperatures so elevated as to result in substantial DMSO alteration, said improvement comprising carrying out the reaction by:
- a. providing a mixture of solid KF particles and a solution, in DMSO, of said alpha-chloropyridine, said mixture containing
- 1. less than such amount of any HF source materials as to provide a total of 0.015 grams of HF per 100 grams of KF,
- 2. a total of less than 0.5 grams of K.sub.2 CO.sub.3 and KHCO.sub.3 per 100 grams of KF,
- 3. less than 0.5 grams of water per 100 grams of DMSO;
- and
- b. intensely stirring said mixture and maintaining the temperature thereof within the range of from about 175.degree. to about 192.degree. .
Dependencies are inferred from the claim text.