[F:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][CH:6]=[CH:5]2.[C:11]([OH:15])(=[O:14])[CH:12]=[CH2:13].C(OC(=O)C)(=O)C>C(O)(=O)C>[F:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][CH:6]=[C:5]2[CH2:13][CH2:12][C:11]([OH:15])=[O:14]Thus, a solution of 5-fluoroindole (1.35 g, 0.010 mol) in 10 mL of acetic acid containing acrylic acid (1.5 mL, 0,022 mol) and acetic anhydride (1.9 mL, 0.02 mol) was heated (oil bath) at 90° C. under Ar for 5 days. The volatiles were then removed in vacuo and the residue was taken up in 3N NaOH. Insoluble material was removed by filtration and the filtrate was acidified with conc. HCl and then extracted with CH2Cl2. The organic extract was dried (Na2SO4) and evaporated to give the product (1.191 g, 57%) as a solid which was used without further purification: IR (neat) 3420, 1710 cm-1 ; 1Hnmr (200 MHz, CDCl3) δ 7.94 (br s, 1H), 7.28-7.18 (m, 3H), 7.05 (d, J=2.5 Hz, 1H), 6.93 (dt, J=9.0, 2.6 Hz, 1H), 3.05 (t, J=7.5 Hz, 2H), 2.73 (t, J=7.6 Hz, 2H).
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