Hydrofluoric Acid → 2,5-Dichloro-3-fluoropyridine

HRID 986368Notes

Reaction equation

HRID 986368 reaction equation
[FH:1].N[C:3]1[C:4]([Cl:10])=[N:5][CH:6]=[C:7]([Cl:9])[CH:8]=1.N([O-])=O.[Na+]>>[Cl:10][C:4]1[C:3]([F:1])=[CH:8][C:7]([Cl:9])=[CH:6][N:5]=1

Participants

4

Reactant 3

HCID 14917Hydrofluoric AcidHCID 27999993-Amino-2,5-dichloropyridineHCID 23668193Sodium Nitrite

Product 1

HCID 109648772,5-Dichloro-3-fluoropyridine

Procedure

To 450 ml (22.5 mol) of hydrogen fluoride in a stainless steel reaction vessel are added at a temperature of -5° to -1° , 163 g (1.0 mol) of 3-amino-2,5-dichloropyridine. Then there are added while stirring at the same temperature 82.8 g (1.2 mol) of sodium nitrite into the solution. The reaction mixture is stirred for 1.5 hours at -5° to -1°, then the temperature is slowly raised to +60° C. After the evolution of gas has ceased, the hydrogen fluoride is distilled off and the residue is taken up in methylene chloride. Ice/water is then added thereto and the cold mixture is neutralized with concentrated ammonium hydroxide solution. The organic phase separated and the water phase is extracted three times with methylene chloride. The organic phases are washed with water, dried over magnesium sulfate, filtered through silica-gel and evaporated. Thus, 141.5 g (85% of the theory) of 2,5-dichloro-3-fluoropyridine are obtained.

Workup

  1. additionThen there are added
  2. temperaturethe temperature is slowly raised to +60° C
  3. distillationthe hydrogen fluoride is distilled off
  4. additionIce/water is then added
  5. customThe organic phase separated
  6. extractionthe water phase is extracted three times with methylene chloride
  7. washThe organic phases are washed with water
  8. dry with materialdried over magnesium sulfate
  9. filtrationfiltered through silica-gel
  10. customevaporated

Sources & evidence

ORD record
ord-b63e412a44eb4e0abee335b749253ee0
Source dataset
uspto-grants-1987_12
Patent number
US04713109

Reaction notes

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