P(Cl)(Cl)(Cl)=O.CN(C)[CH:8]=[O:9].[NH:11]1[C:19]2[C:14](=[CH:15][C:16]([C:20]([O:22][CH3:23])=[O:21])=[CH:17][CH:18]=2)[CH:13]=[CH:12]1.C(=O)([O-])[O-].[K+].[K+]>O>[CH:8]([C:13]1[C:14]2[C:19](=[CH:18][CH:17]=[C:16]([C:20]([O:22][CH3:23])=[O:21])[CH:15]=2)[NH:11][CH:12]=1)=[O:9]A 1.28 ml portion of phosphoryl chloride was added dropwise to 8 ml of N,N-dimethylformamide under ice-cooling, followed by stirring at room temperature for 15 minutes. An 8 ml portion of an N,N-dimethylformamide solution of 2.00 g of methyl 1H-indole-5-carboxylate was added dropwise to this solution under ice-cooling, followed by stirring at room temperature for 1.5 hours. Under ice-cooling, 50 ml of water was added thereto and potassium carbonate was further added until the pH became 12, and the resulting solid was collected by filtration, washed with water and then dried over heating under a reduced pressure to obtain 2.19 g of methyl 3-formyl-1H-indole-5-carboxylate as a pale light brown solid.
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