[NH:1]1[C:9]2[C:4](=[CH:5][CH:6]=[CH:7][CH:8]=2)[CH:3]=[CH:2]1.[Li+].C[Si]([N-][Si](C)(C)C)(C)C.[CH3:20][N:21]1[C:25](=[O:26])[C:24](Br)=[C:23]([Br:28])[C:22]1=[O:29].Cl>O1CCCC1>[Br:28][C:23]1[C:22](=[O:29])[N:21]([CH3:20])[C:25](=[O:26])[C:24]=1[C:3]1[C:4]2[C:9](=[CH:8][CH:7]=[CH:6][CH:5]=2)[NH:1][CH:2]=1A solution containing 1.445 g of indole, dissolved in 29 ml of dry tetrahydrofuran, is held between −20 and −10° C. under argon, and then 26 ml of LiHMDS (1M in hexane) are added, dropwise, over the course of 15 minutes. After 45 minutes at −10° C., the solution is diluted with 15 ml of additional tetrahydrofuran, and a solution containing 2 g of N-methyl-2,3-dibromomaleimide dissolved in 17 ml of tetrahydrofuran is added dropwise over the course of 30 minutes. After 15 minutes at −10° C. and 15 minutes at 0° C., the reaction is stopped by the addition, at 0° C., of 50 ml of 0.3N hydrochloric acid solution. The reaction mixture is extracted with ethyl acetate, and the organic phases are washed with saturated NaCl solution, dried over MgSO4 and then evaporated under reduced pressure. The desired product is precipitated using methanol.
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