Reaktion #453615

Reaktionsgleichung

3-methylbenzimidazol-4-ol

2-Amino-3-nitrophenol

formic-acetic anhydride

2-amino-3-nitrophenol

3-methylbenzotriazol-4-ol

→

title compound

2-Methylamino-3-nitrophenol

Lösungsmittel

CHCl3

THF

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   Einengenwas concentrated in vacuo to a viscous oil which
2. 2
   workup.DISSOLUTIONwas redissolved in THF (12 mL)
3. 3
   workup.ADDITIONtreated dropwise with 2M borane-dimethylsulfide in THF (63 mL) at about -5° C
4. 4
   workup.ADDITIONWhen the addition
5. 5
   Temperaturwas heated
6. 6
   Temperaturto reflux (2 hours)
7. 7
   Temperaturcooled in ice
8. 8
   Sonstigequenched with MeOH (20 mL)
9. 9
   workup.STIRRINGAfter stirring for 1 hour at about 22° C.
10. 10
    Sonstigeanhydrous HCl was bubbled into the solution to acidity it to about pH 2
11. 11
    TemperaturThe mixture was refluxed for 1 hour
12. 12
    Einengenconcentrated in vacuo
13. 13
    workup.DISSOLUTIONThe residue was dissolved in H2O
14. 14
    Temperaturcooled (16 hours)
15. 15
    Sonstigeto produce a dark brown solid
16. 16
    Trocknendried over Na2SO4
17. 17
    Einengenconcentrated in vacuo
18. 18
    Sonstigeto afford a red-brown solid (6.72 g; >95% purity) which

Vorschrift

The title compound was prepared from 2-amino-3-nitrophenol according to a procedure adapted from Tet. Lett. 23, 3315 (1982). 2-Amino-3-nitrophenol (7.7 g, 50 mmol) in dry THF (20 mL) was treated dropwise with formic-acetic anhydride (130 mmol) in THF (10 mL) at about -5° C. under N2 (g). After stirring 3 hours the mixture was concentrated in vacuo to a viscous oil which was redissolved in THF (12 mL) and treated dropwise with 2M borane-dimethylsulfide in THF (63 mL) at about -5° C. When the addition was complete the mixture was heated to reflux (2 hours), cooled in ice and quenched with MeOH (20 mL). After stirring for 1 hour at about 22° C., anhydrous HCl was bubbled into the solution to acidity it to about pH 2. The mixture was refluxed for 1 hour and concentrated in vacuo. The residue was dissolved in H2O, neutralized with conc. NH4OH and cooled (16 hours) to produce a dark brown solid. This wet material was dissolved in CHCl3, dried over Na2SO4 and concentrated in vacuo to afford a red-brown solid (6.72 g; >95% purity) which was used directly in the syntheses of 3-methylbenzimidazol-4-ol and 3-methylbenzotriazol-4-ol (below).

Quelle