6-Chloro-2-benzothiazolamine → 2-Amino-5-chlorobenzenethiol

HRID 1604268Notes

Reaction equation

HRID 1604268 reaction equation
[S-]C#N.[K+].ClC1C=CC(N)=CC=1.BrBr.NC1[S:17][C:18]2[CH:24]=[C:23]([Cl:25])[CH:22]=[CH:21][C:19]=2[N:20]=1.[OH-].[K+]>C(O)(=O)C.O>[Cl:25][C:23]1[CH:22]=[CH:21][C:19]([NH2:20])=[C:18]([SH:17])[CH:24]=1

Participants

8

Reactant 5

HCID 72266-Chloro-2-benzothiazolamineHCID 78124-ChloroanilineHCID 14797Potassium HydroxideHCID 24408BromineHCID 516872Potassium thiocyanate

Product 1

HCID 27375182-Amino-5-chlorobenzenethiol

Reagents, catalysts & solvents 2

HCID 176Acetic AcidSolvent2×HCID 962WaterSolvent2×

Procedure

Potassium thiocyanate (38.8 g, 0.40 mole) and 4-chloroaniline (50.9 g, 0.40 mole) are dissolved in 300 mL of glacial acetic acid. The solution is cooled below 10° C. in an ice bath and while stirring, bromine (10 mL, 0.40 mole) in glacial acetic acid (50 mL) is added dropwise over one hour with the temperature maintained below 10° C. with external cooling. Stirring is continued for an additional 30 minutes. The reaction mixture is stirred at room temperature for 16 hours. The hydrobromide salt of 2-amino-6-chlorobenzothiazole 5 (X=Cl) is washed with hexane (2×25 mL). The salt is dissolved in warm water (300 mL) and the product precipitated by addition of dilute (10%) sodium hydroxide. The crude product is filtered and recrystallized from ethanol (mp 198-200° C., yield 16.47 g, 63.3%). A mixture of 2-amino-6-chlorobenzothiazole 5 (15 g, 0.08 mole), potassium hydroxide (75 g, 1.34 mole), and water (150 mL) is heated with stirring under reflux over nitrogen for 8 hours. The vigorous reaction subsides slowly. The mixture is then diluted with water (20 mL) and filtered. To the filtrate is added 5 N acetic acid with vigorous stirring and cooling until it is just acid to pH paper. The yellow crystals are filtered, washed with cold water and recrystallized from absolute ethanol and decolorized with neutral Norit. Yield of 5-chloro-2-aminobenenethiol (6, X=Cl); 40%; mp 108-110° C. (lit 110° C.).

Workup

  1. temperatureThe solution is cooled below 10° C. in an ice bath
  2. temperaturemaintained below 10° C. with external cooling
  3. stirringStirring
  4. stirringThe reaction mixture is stirred at room temperature for 16 hours
  5. washThe hydrobromide salt of 2-amino-6-chlorobenzothiazole 5 (X=Cl) is washed with hexane (2×25 mL)
  6. dissolutionThe salt is dissolved in warm water (300 mL)
  7. customthe product precipitated by addition
  8. additionof dilute (10%) sodium hydroxide
  9. filtrationThe crude product is filtered
  10. customrecrystallized from ethanol (mp 198-200° C., yield 16.47 g, 63.3%)
  11. temperatureis heated
  12. stirringwith stirring
  13. temperatureunder reflux over nitrogen for 8 hours
  14. customThe vigorous reaction subsides slowly
  15. filtrationfiltered
  16. additionTo the filtrate is added 5 N acetic acid
  17. stirringwith vigorous stirring
  18. temperaturecooling until it
  19. filtrationThe yellow crystals are filtered
  20. washwashed with cold water
  21. customrecrystallized from absolute ethanol and decolorized with neutral Norit
  22. custommp 108-110° C. (lit 110° C.)

Sources & evidence

ORD record
ord-5becfa6924bf4a20abdbc4defa8c38fb
Source dataset
uspto-grants-1999_11
Patent number
US05994349

Reaction notes

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