Phosphorus oxychloride → Ethyl 4,6-dichloropyridine-2-carboxylate

HRID 882743Notes

Reaction equation

HRID 882743 reaction equation
[CH2:1]([O:3][C:4](=[O:13])[C:5]1[N+:6]([O-])=[CH:7][CH:8]=[C:9]([Cl:11])[CH:10]=1)[CH3:2].P(Cl)(Cl)([Cl:16])=O>>[CH2:1]([O:3][C:4](=[O:13])[C:5]1[CH:10]=[C:9]([Cl:11])[CH:8]=[C:7]([Cl:16])[N:6]=1)[CH3:2]

Participants

3

Reactant 2

HCID 24813Phosphorus oxychlorideHCID 59258554Ethyl 4-chloro-1-oxo-1lambda~5~-pyridine-2-carboxylate

Product 1

HCID 52982911Ethyl 4,6-dichloropyridine-2-carboxylateYield 64%

Conditions

Temperature
0 °C

Procedure

4-Chloropicolinic acid ethyl ester N-oxide (1.6 g, 8 mmol) was added to 4 mL of phosphorus oxychloride at 0° C. and stirred at 0° C. for one hour. The solution was then heated at 100° C. for four hours. Excess POCl3 was removed in vacuo, and the residue was dissolved in ethyl acetate, washed with cold sodium bicarbonate solution, and extracted with ethyl acetate. Removal of the solvent gave 4,6-dichloropicolinic acid ethyl ester (compound A) as an off-white solid (1.12 g, 64%). The methyl ester can be made by an analogous procedure.

Workup

  1. temperatureThe solution was then heated at 100° C. for four hours
  2. customExcess POCl3 was removed in vacuo
  3. dissolutionthe residue was dissolved in ethyl acetate
  4. washwashed with cold sodium bicarbonate solution
  5. extractionextracted with ethyl acetate
  6. customRemoval of the solvent

Sources & evidence

ORD record
ord-a55ce29bd4fc4f87b8dc4536635736cd
Source dataset
uspto-grants-2012_08
Patent number
US08236795B2

Reaction notes

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