[OH:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][CH:6]=[CH:5]2.C([O-])([O-])=O.[K+].[K+].I[CH2:18][CH3:19].ClCCl.CO>CC(C)=O>[CH2:18]([O:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][CH:6]=[CH:5]2)[CH3:19]A mixture of commercially available 5-hydroxy-indole (18 g, 13.5 mmol), anhydrous K2CO3 (93.5 g, 5 equiv) and iodoethane (40.5 ml, 3.75 equiv) in acetone (180 mL) is stirred at 50° C. under argon. When TLC (dichloromethane-methanol, 95:5) indicates the disappearance of 5-hydroxy-indole (4 days), the mixture is filtered, the solid is washed with acetone, then the filtrate is concentrated to give 17.67 g (90%) of the title compound, which is sufficiently pure to be used in the next step. M.p. 144-146° C. (from ethanol).
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