Claims
- 1. A method of preparing a product compound having the formula ##STR3## wherein X is Br or Cl, which comprises contacting a starting compound having the formula ##STR4## wherein each X is individually Br or Cl and Y is F, Cl or Br with an effective amount of KF in a polar aprotic diluent at an effective temperature of from 50.degree. C. to the boiling point of the diluent, optionally in the presence of a phase-transfer catalyst, removing the product compound by distillation essentially as it is formed, and, optionally, adding additional starting compound as the product compound is removed.
- 2. Method of claim 1 wherein the 2,3-dihalopyridine compound is 2,3,5-trichloropyridine and the product is 2,3-difluoro-5-chloropyridine.
- 3. Methood of claim 1 wherein the 2,3-dihalopyridine compound is 2,3,5-tribromopyridine and the product is 2,3-difluoro-5-bromopyridine.
- 4. Method of claim 1 wherein the fluoride salt is KF and the reaction is carried out in the presence of (a) a phase-transfer catalyst and optionally (b) an acid scavenger.
- 5. Method of claim 1 wherein the diluent is dimethylsulfoxide, sulfolane or N-methylpyrrolidinone.
- 6. Method of claim 1 wherein the salt is KF and the reaction temperature is from 175.degree. C. up to the boiling point of the diluent.
- 7. Method of claim 1 wherein the reaction is carried out at a pressure from 50 to 300 mm Hg.
- 8. Method of claim 4 wherein the phase-transfer catalyst is a quaternary ammonium halide, a crown ether, or tris(3,6-dioxaheptyl)amine.
CROSS REFERENCE TO RELATED APPLICATION
This is is a continuation of application Ser. No. 901,717, filed Aug. 28, 1986 now abandoned which application is a continuation-in-part of Ser. No. 665,588 filed Oct. 29, 1984 abandoned which in turn was a continuation-in-part of Ser. No. 564,800 filed Dec. 23, 1983, now abandoned.
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
1340421 |
Dec 1973 |
GBX |
Non-Patent Literature Citations (6)
Entry |
Finger et al., J. Organic Chem., 28, 1666-1668 (1963). |
Chambers et al., Proc. Chem. Soc., 1964, p. 83. |
Chambers et al., J. Chem. Soc., 1964, 3573-3576. |
Newkome and Paudler, Contemporary Heterocyclic Chemistry, pp. 262-264. |
Banks et al., J. Chem. Soc., 1865, 594-597. |
Abramovitch, Pyridine and its Derivatives Part 2 Supplement, pp. 422-423. |
Continuations (1)
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Number |
Date |
Country |
Parent |
901717 |
Aug 1986 |
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Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
665588 |
Oct 1984 |
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Parent |
564800 |
Dec 1983 |
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