Process for making 2-chloro-5-methylpyridine
Processes for the preparation of 2-chloro-5-methylpyridine are described.
1. A process for preparing 2-chloro-5-methylpyridine, the process comprising the step of:
a) contacting 3-methylpyridine N-oxide in a diluent, at a first temperature of about −20° C. to about 20° C., with phosphoryl oxychloride (POCl 3 ), and 2,2,6,6-tetramethylpiperidine.
2. The process of claim 1 further comprising the step of
b) contacting the 3-methylpyridine N-oxide in the diluent with aluminum chloride (AlCl 3 ) prior to contacting with POCl 3 , and the 2,2,6,6-tetramethylpiperidine.
3. The process of claim 2 wherein the amount of AlCl 3 per mole of 3-methylpyridine N-oxide is about 0.1 mole to about 0.3 mole.
4. The process of claim 2 wherein the amount of AlCl 3 per mole of 3-methylpyridine N-oxide is about 0.2 mole to about 0.25 mole.
5. The process of claim 1 wherein the diluent is selected from pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, petroleum ether, naphtha, ligroin, benzene, toluene, xylenes, methylene chloride, chloroform, tetrachloromethane, 1,2-dichloroethane, chlorobenzene, dichlorobenzene, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, methyl tert-butyl ether, glycol dimethyl ether, diglycol dimethyl ether, tetrahydrofuran, dioxane, methyl acetate, ethyl acetate, propyl acetate, butyl acetate amyl acetate, acetonitrile, and propionitrile.
6. The process of claim 1 wherein the diluent is methylene chloride.
7. The process of claim 1 wherein the amount of POCl 3 per mole of 3-methylpyridine N-oxide is about 1 to about 5 moles.
8. The process of claim 1 wherein the amount of POCl 3 per mole of 3-methylpyridine N-oxide is about 1.5 to about 2.5 moles.
9. The process of claim 1 wherein the amount of POCl 3 per mole of 3-methylpyridine N-oxide is about 2 moles.
10. The process of claim 1 wherein the amount of the 2,2,6,6-tetramethylpiperidine per mole of 3-methylpyridine N-oxide is about 1 to about 5 moles.
11. The process of claim 1 wherein the amount of the 2,2,6,6-tetramethylpiperidine per mole of 3-methylpyridine N-oxide is about 1.5 to about 2.5 moles.
12. The process of claim 1 wherein the amount of the 2,2,6,6-tetramethylpiperidine per mole of 3-methylpyridine N-oxide is about 2 moles.
13. The process of claim 1 further comprising the step of
b) heating the resulting mixture from step a) to a second temperature while removing a portion of the diluent by distillation.
14. The process of claim 2 further comprising the step of
c) holding the mixture resulting from step b) at the second temperature for a period of time, wherein the second temperature is from about 50° C. to about 150° C.