Reacción #62031

Ecuación de reacción

potassium acetate

isoamyl nitrite

ester

methyl 2-amino-3-methylbenzoate

acetic anhydride

chloroform

→

methyl 1H-indazole-7-carboxylate hydrochloride

Rendimiento 68.0%

Condiciones de reacción

Tratamiento posterior

1. 1
   Temperaturawhile maintaining the temperature below 40° C
2. 2
   workup.ADDITIONwas added
3. 3
   TemperaturaThe reaction mixture was heated
4. 4
   Temperaturaat reflux for 24 h
5. 5
   LavadoThe reaction mixture was washed with a saturated, aqueous solution of sodium bicarbonate
6. 6
   Secadodried over sodium sulfate
7. 7
   Concentraciónconcentrated
8. 8
   workup.ADDITIONMethanol (100 mL) and 6 N hydrochloric acid (100 mL) were added to the residue
9. 9
   Temperaturathe mixture was maintained for 18 h at rt
10. 10
    OtroThe volatiles were removed under reduced pressure
11. 11
    Otrothe residue was triturated with ethyl acetate (100 mL)
12. 12
    OtroThe product was isolated by filteration
13. 13
    Lavadowashed with ethyl acetate (20 mL)
14. 14
    Otrodried

Procedimiento

To a solution of the ester (17.5 g, 106 mmol) in chloroform (300 mL) was added acetic anhydride (22.6 mL, 239 mmol, 2.3 eq) while maintaining the temperature below 40° C. The reaction mixture was maintained at room temperature for 1 h when potassium acetate (3.00 g, 30.6 mmol, 0.3 eq) and isoamyl nitrite (30.6 mL, 228 mmol, 2.2 eqiv) was added. The reaction mixture was heated at reflux for 24 h and was allowed to cool to room temperature. The reaction mixture was washed with a saturated, aqueous solution of sodium bicarbonate, dried over sodium sulfate, and concentrated. Methanol (100 mL) and 6 N hydrochloric acid (100 mL) were added to the residue and the mixture was maintained for 18 h at rt. The volatiles were removed under reduced pressure and the residue was triturated with ethyl acetate (100 mL). The product was isolated by filteration, washed with ethyl acetate (20 mL), and dried to provide 15.3 g (68%) of methyl 1H-indazole-7-carboxylate hydrochloride. 1H NMR (500 MHz, DMSO-d6) δ 13.3 (bs, 1H), 8.26 (d, 1H), 8.12 (d, 1H), 8.25 (dd, 1H), 7.27 (t, 1H), 3.97 (s, 3H); MS (APCI) m/z 177 (M++1).

Fuente