[CH2:1]([CH:3]([C:6]1[C:11]2[N:12]([CH3:16])[C:13](=O)[NH:14][C:10]=2[C:9]([C:17]([O:19][CH3:20])=[O:18])=[CH:8][CH:7]=1)[CH2:4][CH3:5])[CH3:2].P(Cl)(Cl)([Cl:23])=O>C1(C)C=CC=CC=1>[Cl:23][C:13]1[N:12]([CH3:16])[C:11]2[C:6]([CH:3]([CH2:4][CH3:5])[CH2:1][CH3:2])=[CH:7][CH:8]=[C:9]([C:17]([O:19][CH3:20])=[O:18])[C:10]=2[N:14]=1A mixture of methyl 7-(1-ethylpropyl)-1-methyl-2-oxo-2,3-dihydro-1H-benzimidazole-4-carboxylate (1.30 g, 4.70 mmol) and phosphoryl chloride (10 ml) was heated at 100° C. for 3 h. The mixture was diluted with toluene and concentrated in vacuo to remove excess reagent. The residue was diluted with aqueous saturated sodium bicarbonate and extracted with ethyl acetate. The extracts were washed with water, dried over magnesium sulfate and concentrated in vacuo. The residue was purified by chromatography on column silica gel with a 10% ethyl acetate/n-hexane to give 1.18 g (4.00 mmol, 85%) of the title compound as a colorless oil.
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