Sodium Hydroxide → 2,5,6-Trichloro-1H-benzimidazole
Reaction equation
[Cl:1][C:2]1[C:11]([Cl:12])=[CH:10][C:5]2[NH:6][C:7](=O)[NH:8][C:4]=2[CH:3]=1.[OH-].[Na+].O=P(Cl)(Cl)[Cl:17]>>[Cl:17][C:7]1[NH:6][C:5]2[CH:10]=[C:11]([Cl:12])[C:2]([Cl:1])=[CH:3][C:4]=2[N:8]=1Participants
4
Procedure
Thoroughly dried 5,6-dichloro-1,3-dihydro-benzoimidazol-2-one (28.4 g, 0.14 mol) was suspended in POCl3 (75 mL). The reaction solution was heated to reflux temperature for 3 hours and cooled to room temperature. The solution was poured into crushed ice/water (1.5 L) slowly with sufficient stirring. The solution was neutralized to pH=7.0 with NaOH. The precipitated solid was collected by filtration, washed with water, and dried to afford the title compound (27.9 g, 90%). The crude product was used in the following reaction without further purification.