Hydrogen Bromide → 2-Amino-6-benzothiazolol

HRID 1639553Notes

Reaction equation

HRID 1639553 reaction equation
C([O:3][C:4]1[CH:13]=[CH:12][C:7]2[N:8]=[C:9]([NH2:11])[S:10][C:6]=2[CH:5]=1)C.Br>C(O)(=O)C.O.ClCCl>[NH2:11][C:9]1[S:10][C:6]2[CH:5]=[C:4]([OH:3])[CH:13]=[CH:12][C:7]=2[N:8]=1

Participants

6

Reactant 2

HCID 260Hydrogen BromideHCID 7192Amino-6-ethoxybenzothiazole, 2-

Product 1

HCID 334622-Amino-6-benzothiazololYield 88.5%

Reagents, catalysts & solvents 3

HCID 176Acetic AcidSolventHCID 962WaterSolventHCID 6344DichloromethaneSolvent

Procedure

To a solution of 7 g of 6-ethoxy-1,3-benzothiazol-2-amine (commercial) in 65 cm3 of glacial acetic acid are added 130 cm3 of a 48% solution of hydrobromic acid in water. The solution is refluxed for about 20 hours. After concentrating to dryness under reduced pressure (13 kPa), the residue is taken up in 50 cm3 of water and the pH of the solution is brought to about 8 by addition of solid sodium hydrogen carbonate. The mixture is extracted with four times 250 cm3 of ethyl acetate and the combined organic phases are washed with three times 20 cm3 of saturated aqueous sodium chloride solution, dried over magnesium sulfate, filtered and concentrated to dryness under reduced pressure (13 kPa). The solid obtained is taken up in 20 cm3 of dichloromethane, filtered off by suction, washed with three times 10 cm3 of dichloromethane and then three times 20 cm3 of diethyl ether, and dried under reduced pressure (13 kPa) over phosphorus pentoxide. 5.3 g of 2-amino-1,3-benzothiazol-6-ol are thus obtained in the form of a pink powder, the characteristics of which are as follows:

Workup

  1. temperatureThe solution is refluxed for about 20 hours
  2. concentrationAfter concentrating to dryness under reduced pressure (13 kPa)
  3. additionthe pH of the solution is brought to about 8 by addition of solid sodium hydrogen carbonate
  4. extractionThe mixture is extracted with four times 250 cm3 of ethyl acetate
  5. washthe combined organic phases are washed with three times 20 cm3 of saturated aqueous sodium chloride solution
  6. dry with materialdried over magnesium sulfate
  7. filtrationfiltered
  8. concentrationconcentrated to dryness under reduced pressure (13 kPa)
  9. customThe solid obtained
  10. filtrationfiltered off by suction
  11. washwashed with three times 10 cm3 of dichloromethane
  12. dry with materialthree times 20 cm3 of diethyl ether, and dried under reduced pressure (13 kPa) over phosphorus pentoxide

Sources & evidence

ORD record
ord-f3ce332947b940fab405ef412d14c606
Source dataset
uspto-grants-2012_02
Patent number
US08110571B2

Reaction notes

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