反应详情

温度

-10 °C

Nitric acid (70%, 2.50 ml, 0.0389 mol) is added dropwise at −10° C. to a solution of 4-fluoro-1,3-benzoxazol-2(3H)-one (Step 4, 5.95 g, 0.0389 mol) in concentrated sulfuric acid (60 ml). The reaction is stirred at −10° C. for 30 minutes and then poured into ice water. The resulting precipitate is collected by filtration and dried under reduced pressure to give desired product contaminated with approximately 10-15% of the undesired 5-nitro isomer (7.2 g, 93%); mp 177-9° C.

1. filtrationThe resulting precipitate is collected by filtration
2. customdried under reduced pressure