Phosphorus oxychloride → 2-Chloro-5-methyl-1,3-benzoxazole

HRID 553455Notes

Reaction equation

HRID 553455 reaction equation
[CH3:1][C:2]1[CH:3]=[CH:4][C:5]2[O:9][C:8](S)=[N:7][C:6]=2[CH:11]=1.O=P(Cl)(Cl)[Cl:14].P(Cl)(Cl)(Cl)(Cl)Cl>C(Cl)Cl>[Cl:14][C:8]1[O:9][C:5]2[CH:4]=[CH:3][C:2]([CH3:1])=[CH:11][C:6]=2[N:7]=1

Participants

5

Reactant 3

HCID 24813Phosphorus oxychlorideHCID 24819Phosphorus pentachlorideHCID 178423563HCID 178423563, compound

Product 1

HCID 99896072-Chloro-5-methyl-1,3-benzoxazoleYield 107.6%

Reagents, catalysts & solvents 1

HCID 6344DichloromethaneSolvent

Procedure

To a suspension of 5-methylbenzo[d]oxazole-2-thiol (1.0 g, 6.1 mmol.) in POCl3 (11.7 g, 76.4 mmol.) at room temperature was added PCl5 (1.9 g, 9.15 mmol.) along with CH2Cl2 (10 mL). After 4 h of stirring at room temperature, the reaction mixture was concentrated to remove excess POCl3, and the residue was treated with Na2CO3 solution until ˜pH 8 was reached. The aqueous phase was extracted with CH2Cl2. The combined organic extracts were dried over Na2SO4, filtered and concentrated to afford 2-chloro-5-methylbenzo[d]oxazole (1.1 g crude product) which was used without further purification. MS (ESI) m/e (M+H+) 168.

Workup

  1. concentrationthe reaction mixture was concentrated
  2. customto remove excess POCl3
  3. additionthe residue was treated with Na2CO3 solution until ˜pH 8
  4. extractionThe aqueous phase was extracted with CH2Cl2
  5. dry with materialThe combined organic extracts were dried over Na2SO4
  6. filtrationfiltered
  7. concentrationconcentrated

Sources & evidence

ORD record
ord-54d336af942a49dda9acf8f1a9c42fe2
Source dataset
uspto-grants-2011_11
Patent number
US08048862B2

Reaction notes

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