反应详情

Treatment of 1-(4-fluoro-2,3-dihydro-indol-1-yl)-ethanone, prepared from 4-fluoroindole (See e.g., EP 0645385A1), with concentrated H2SO4 and fuming HNO3 in glacial acetic acid gave 1-(4-fluoro-5-nitro-2,3-dihydro-indol-1-yl)-ethanone. Deprotection of the acetyl group with Na2S in aqueous ethanol provided 4-fluoro-5-nitro-2,3-dihydro-1H-indole, which was treated with 2,3-dicyano-5,6-dichloro-parabenzoquinone (DDQ) to provide 4-fluoro-5-nitroindole. A subsequent hydrogenation over Pd/C gave 5-amino-4-fluoroindole.