Cl[C:2](=[O:8])[C:3]([O:5][CH2:6][CH3:7])=[O:4].[Cl:9][C:10]1[CH:18]=[C:17]2[C:13]([CH:14]=[C:15]([C:20]([O:22][CH2:23][CH3:24])=[O:21])[N:16]2[CH3:19])=[CH:12][CH:11]=1.ClCCl.O>ClCCCl.[Ti](Cl)(Cl)(Cl)Cl>[Cl:9][C:10]1[CH:18]=[C:17]2[C:13]([C:14]([C:2](=[O:8])[C:3]([O:5][CH2:6][CH3:7])=[O:4])=[C:15]([C:20]([O:22][CH2:23][CH3:24])=[O:21])[N:16]2[CH3:19])=[CH:12][CH:11]=14 ml (36.4 mmol) of titanium(IV) chloride are added to a solution of 4 ml (36 mmol) of ethyl chlorooxoacetate in 100 ml of 1,2-dichloroethane. The reaction mixture is stirred for 30 min at room temperature, 7.8 g (32.8 mmol) of ethyl 6-chloro-1-methyl-1H-indole-2-carboxylate are then added and the reaction mixture is stirred for 4 hours at room temperature. The mixture is cooled and 200 ml of dichloromethane and 100 ml of water are added. The organic phase is separated by settling, washed with water, dried over sodium sulphate, filtered and concentrated under reduced pressure and the residue is purified by chromatography on a column of silica gel. 9.4 g (27.7 mmol) of product are isolated.
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