Reacción #322474

Ecuación de reacción

H2SO4

3,5-dimethylaniline

hydroxyamine hydrochloride

sodium sulfate

ethyl acetate

→

title compound

Rendimiento 20.0%

4,6-dimethylisatin

Rendimiento 20.0%

Disolventes

water

HCl

water

HCl

Condiciones de reacción

Tratamiento posterior

1. 1
   TemperaturaThe mixture was heated to vigorous boiling
2. 2
   FiltraciónIt was filtered
3. 3
   Lavadowashed by water
4. 4
   Otrodried
5. 5
   Otroto leave pale yellow solid
6. 6
   Otrokept at 50° C
7. 7
   workup.ADDITIONAfter the addition
8. 8
   Temperaturathe solution was heated to 80° C. for 15 min
9. 9
   TemperaturaIt was cooled to room temperature
10. 10
    workup.WAITAfter standing for 0.5 h
11. 11
    Filtraciónit was filtered
12. 12
    Lavadowashed with water
13. 13
    Otrodried
14. 14
    Otroto leave a yellow solid
15. 15
    Filtraciónfiltered
16. 16
    Temperaturacooled to room temperature
17. 17
    OtroThe crystalline solid was collected
18. 18
    Otrodried

Procedimiento

The procedure of Varma and Singh, Ind. J. Chem. 296:578-81 (1990), was adapted. To a solution of tribromoacetaldehyde CBr3CHO (6.80 g, 24 mmol, Aldrich) in water (60 mL) and 1N HCl (2 mL) was added successively sodium sulfate (6.20 g, 43 mmol), a solution of 3,5-dimethylaniline (2.54 g, 21 mmol) in 1N HCl (40 mL), and a solution of hydroxyamine hydrochloride (5.50 g, 79 mmol) in water (25 mL). The mixture was heated to vigorous boiling and kept boiling for 10 min then cooled in ice bath to room temperature. It was filtered, washed by water, dried to leave pale yellow solid. The solid was added portionwise into concentrated H2SO4 (50 mL) kept at 50° C. After the addition, the solution was heated to 80° C. for 15 min. It was cooled to room temperature, and added into ice water (450 mL). After standing for 0.5 h, it was filtered and washed with water and dried to leave a yellow solid. The solid was boiled with ethyl acetate (180 mL), filtered and cooled to room temperature. The crystalline solid was collected and dried to give the title compound (752 mg, 20%) containing a 2% impurity by NMR. Recrystallization from DMSO/H2O afforded pure title compound as needles: mp 220°-2° C. IR (KBr, cm-1) 3439, 3211, 1762, 1729, 1628. 1H NMR (DMSO-d6): δ2.821 (s, 3H); 2.380 (s, 3H); 6.517 (s, 1H); 6.673 (s, 1H); 10.931 (s, 1H). LRMS: calcd for C10H9NO2 m/z: 175; found: 175. Purity: >97.4% by HPLC.

Fuente