Reaction #724812

Reaction equation

sodium nitrite

sodium dithionite

sodium sulfite

potassium chloride

1E

8-amino-3,4-dihydro-2,5-dimethyl-2H-1-benzopyran

hydrochloric acid

→

8-hydrazino-3,4-dihydro-2,5-dimethyl-2H-1-benzopyran

Solvents

water

water

Conditions

Workup

1. 1
   TemperatureThen the mixture was cooled to 0° C.
2. 2
   workup.STIRRINGThe resulting mixture was stirred at 0° C. for 30 minutes
3. 3
   workup.STIRRINGstirred at room temperature for three hours
4. 4
   workup.STIRRINGthe mixture was stirred at room temperature for 18 hours
5. 5
   TemperatureThe stirred mixture was heated to 75° C.
6. 6
   workup.STIRRINGthe mixture was stirred at 75° C. for 15 minutes
7. 7
   Temperaturechilled to 0° C.
8. 8
   Filtrationfiltered
9. 9
   OtherThe solid was dried
10. 10
    workup.ADDITIONmixed with 300 ml of methanol
11. 11
    workup.STIRRINGThe resulting slurry was stirred
12. 12
    Temperaturecooled to -10° C. while excess anhydrous hydrogen chloride
13. 13
    workup.ADDITIONwas added
14. 14
    workup.STIRRINGThe resulting mixture was stirred to 5° C.
15. 15
    Otherthe methanol was evaporated
16. 16
    Extractionextracted with ether
17. 17
    DryingThe extract was dried (MgSO4)
18. 18
    Filtrationfiltered
19. 19
    Concentrationconcentrated to dryness at 25° C.

Procedure

23 g of 1E was mixed with 60 ml of concentrated hydrochloric acid and the mixture was warmed to 70° C., then stirred to room temperature. Then the mixture was cooled to 0° C. and 120 g of ice water was added, followed by addition, drop-by-drop over 15 minutes, of a solution of 9.9 g of sodium nitrite in 30 ml of water. The resulting mixture was stirred at 0° C. for 30 minutes, poured into a cold (0° C.) mixture of 120 g of sodium sulfite in 450 ml of water, and stirred at room temperature for three hours. Then 22.6 g of sodium dithionite was added in portions to the stirred mixture, at room temperature and the mixture was stirred at room temperature for 18 hours. The stirred mixture was heated to 75° C., 125 g of potassium chloride was added, the mixture was stirred at 75° C. for 15 minutes and then chilled to 0° C. and filtered. The solid was dried and mixed with 300 ml of methanol. The resulting slurry was stirred and cooled to -10° C. while excess anhydrous hydrogen chloride was added. The resulting mixture was stirred to 5° C., the methanol was evaporated therefrom, and the residue was taken up in 300 ml of water. The resulting mixture was made basic with 50% aqueous sodium hydroxide, and extracted with ether. The extract was dried (MgSO4), filtered and concentrated to dryness at 25° C. and 30 Torr, to give 8-hydrazino-3,4-dihydro-2,5-dimethyl-2H-1-benzopyran (1F), as an amber syrup.

Source