反应详情

温度

0 °C

A solution of sodium nitrite (3.16 g, 45.8 mmol) in water 30 ml was added dropwise over 30 minutes to a stirred suspension of 4-amino-2-bromoanisole (Desc. 4(a); 7.31 g, 36.2 mmol) in concentrated hydrochloric acid (50 ml), maintaining the temperature below 0° C. The mixture was stirred at ca. 0° C. for 30 minutes then added portionwise to a suspension of tin(II) chloride dihydrate (36.87 g, 163 mmol) in concentrated hydrochloric acid (50 ml) at -10° C. The resulting thick paste was stirred at -2° C. for 15 minutes, allowed to warm to room temperature over 20 minutes and stirred at room temperature for a further 20 minutes. The reaction mixture was recooled, basified with 10M sodium hydroxide solution and extracted with ethyl acetate (2×250 ml). The extracts were washed with brine (250 ml), combined, dried (MgSO4) and concentrated in vacuo to afford 3-bromo-4-methoxyphenylhydrazine (7.27 g, 93%); δH (250MHz, CDCl3) 3.84 (3H, s, ArOCH3), 6.75 (1H, dd, 8.8, 2.6Hz, 6-H), 6.83 (1H, d, 8.8Hz, 5-H), 7.11 (1H, d, 2.6Hz, 2-H).

1. temperaturemaintaining the temperature below 0° C
2. stirringThe resulting thick paste was stirred at -2° C. for 15 minutes
3. temperatureto warm to room temperature over 20 minutes
4. stirringstirred at room temperature for a further 20 minutes
5. extractionextracted with ethyl acetate (2×250 ml)
6. washThe extracts were washed with brine (250 ml)
7. dry with materialdried (MgSO4)
8. concentrationconcentrated in vacuo