Reacción #81990

Ecuación de reacción

NaHCO3

2,4-dibromo-6-nitroaniline

SnCl2.2H2O

ethanol

→

3,5-Dibromo-1,2-diaminobenzene

Disolventes

—

hexanes

ethyl acetate

ethyl acetate

Condiciones de reacción

Tratamiento posterior

1. 1
   OtroAll the starting material had reacted
2. 2
   workup.ADDITIONpoured into 20 mL
3. 3
   Otrocrushed ice
4. 4
   workup.ADDITIONwas added (foaming!)
5. 5
   Filtraciónfiltered
6. 6
   Extracciónthe filtrate extracted with 3×25 mL ethyl acetate
7. 7
   Lavadothe combined organic extracts washed with sat'd NaCl solution
8. 8
   SecadoThe organic phase was dried (MgSO4), vacuum
9. 9
   Filtraciónfiltered
10. 10
    Otrothe solvent rotary evaporated
11. 11
    Otroto yield a pale yellow oil which
12. 12
    Otrocrystallized
13. 13
    Otroto yield 400 mg (89%)

Procedimiento

3,5-Dibromo-1,2-diaminobenzene was prepared using an adaptation of the method of Bellamy, et al. (Bellamy, F. D. et al., Tetrahedron Lett. 25: 839 (1984)). A mixture of 2,4-dibromo-6-nitroaniline (500 mg, 1.69. mmol) and SnCl2.2H2O (1.90 g, 8.45 mmol) dissolved in 5 mL ethyl acetate and 2 mL absolute ethanol under N2 was heated at 70° C. for 1 h. All the starting material had reacted as evidenced by TLC (silica gel, 3:1 hexanes:ethyl acetate). The reaction was allowed to cool to room temperature and poured into 20 mL crushed ice. Sufficient sat'd NaHCO3 solution was added (foaming!) to bring the pH to 5. The thick yellow white emulsion was vacuum filtered and the filtrate extracted with 3×25 mL ethyl acetate and the combined organic extracts washed with sat'd NaCl solution. The organic phase was dried (MgSO4), vacuum filtered and the solvent rotary evaporated to yield a pale yellow oil which crystallized on standing to yield 400 mg (89%). 1H NMR (CDCl3) δ 3.62 (br s, 4H, 2(NH2)); 6.78 (d, J=1.8, 1H, H-6); 7.01 (d, J=1.8, 1H, H-4).

Fuente