Reaktion #81990

Reaktionsgleichung

NaHCO3

2,4-dibromo-6-nitroaniline

SnCl2.2H2O

ethanol

→

3,5-Dibromo-1,2-diaminobenzene

Lösungsmittel

—

hexanes

ethyl acetate

ethyl acetate

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeAll the starting material had reacted
2. 2
   workup.ADDITIONpoured into 20 mL
3. 3
   Sonstigecrushed ice
4. 4
   workup.ADDITIONwas added (foaming!)
5. 5
   Filtrationfiltered
6. 6
   Extraktionthe filtrate extracted with 3×25 mL ethyl acetate
7. 7
   Waschenthe combined organic extracts washed with sat'd NaCl solution
8. 8
   TrocknenThe organic phase was dried (MgSO4), vacuum
9. 9
   Filtrationfiltered
10. 10
    Sonstigethe solvent rotary evaporated
11. 11
    Sonstigeto yield a pale yellow oil which
12. 12
    Sonstigecrystallized
13. 13
    Sonstigeto yield 400 mg (89%)

Vorschrift

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).

Quelle