P(Cl)(Cl)(Cl)=O.[OH:6][C:7]1[CH:15]=[CH:14][CH:13]=[C:12]2[C:8]=1[CH:9]=[CH:10][NH:11]2.[OH-].[Na+].Cl.CN(C)[CH:21]=[O:22]>O>[OH:6][C:7]1[CH:15]=[CH:14][CH:13]=[C:12]2[C:8]=1[C:9]([CH:21]=[O:22])=[CH:10][NH:11]2
Phosphorous oxychloride 7.35 ml was added dropwise to dry dimethylformamide 15 ml under cooling in ice-methanol bath and the mixture was stirred for 15 min. Then, a solution of the 4-hydroxyindole 5.0 g in dry dimethylformamide 10 ml was added dropwise to the mixture under cooling in ice and the mixture was stirred for 2 h at room temperature. Water was added under cooling in ice to the mixture, which was made alkaline with a 30% aqueous sodium hydroxide solution and was stirred for 15 min. Then, the mixture was acidified to pH 4 with 5N-HCl and the precipitate was collected by filtration, washed with water and dried to give the titled compound 4.99 g as crude crystalline materials. Yield 82%. Crude crystalline materials are recrystallized from methanol to give yellow crystals m.p. 190-193° C.
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