Phosphorus trichloride → 2,6-Dichlorobenzoxazole

HRID 650694Notes

Reaction equation

HRID 650694 reaction equation
[Cl:1][C:2]1[CH:10]=[CH:9][C:5]2[N:6]=[CH:7][O:8][C:4]=2[CH:3]=1.P(Cl)(Cl)[Cl:12].[Cl-].[Cl-].[Cl-].[Al+3].ClCl>P(Cl)(Cl)(Cl)=O>[Cl:12][C:7]1[O:8][C:4]2[CH:3]=[C:2]([Cl:1])[CH:10]=[CH:9][C:5]=2[N:6]=1

Participants

6

Reactant 4

HCID 24387Phosphorus trichlorideHCID 24526Chlorine4×HCID 6451240Aluminum(III) ChlorideHCID 93503626-Chlorobenzoxazole

Product 1

HCID 771752,6-DichlorobenzoxazoleYield 1,931.6%

Reagents, catalysts & solvents 1

HCID 24813Phosphorus oxychlorideSolvent

Conditions

Temperature
100 °C

Procedure

10 g (0.065 mol) of 6-chlorobenzoxazole, 0.45 g of phosphorus trichloride and 0.09 g of anhydrous aluminum trichloride were initially charged in 30 ml of phosphorus oxychloride (POCl3). With heating and stirring, chlorine gas was introduced at a rate of 0.6 equivalent of chlorine per hour. After an internal temperature of 80° C. had been reached, the stream of chlorine gas was reduced to 0.6 equivalent of chlorine per 6 hours, and the temperature was increased to 100° C. The reaction was monitored by gas chromatography. After all of the starting material had been consumed, most of the POCl3 was distilled off and the residue was subjected to fractional distillation under reduced pressure. This gave a pure fraction of 11.9 g of the 2,6-dichlorobenzoxazole, which solidifies on cooling (GC>99% pure) (>97% of theory).

Workup

  1. temperatureWith heating
  2. customAfter an internal temperature of 80° C.
  3. customAfter all of the starting material had been consumed, most of the POCl3
  4. distillationwas distilled off
  5. distillationthe residue was subjected to fractional distillation under reduced pressure

Sources & evidence

ORD record
ord-d95e0b973a8842ecbf5ff31f0bd8edfb
Source dataset
uspto-grants-2001_08
Patent number
US06274739B1

Reaction notes

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