[N:1]1[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][C:4]=2[NH:3][C:2]=1[CH2:10][CH2:11][C:12]1[CH:13]=[C:14]([OH:18])[CH:15]=[CH:16][CH:17]=1.C([O-])([O-])=O.[K+].[K+].[CH2:25](I)[CH3:26].C(C1C2NC(CC)=NC=2C=CC=1)C>CN(C=O)C>[N:1]1[C:5]2[CH:6]=[CH:7][CH:8]=[CH:9][C:4]=2[NH:3][C:2]=1[CH2:10][CH2:11][C:12]1[CH:17]=[CH:16][CH:15]=[C:14]([O:18][CH2:25][CH3:26])[CH:13]=1
A 100 mL flask fitted with a stir-bar and septum with an Ar inlet was charged with benzimidazole 69 (2.00 g, 8.39 mmol), K2CO3 (1.74 g, 12.6 mmol), and DMF (20 mL). Ethyl iodide (1.44 g, 0.74 mL, 9.23 mmol) was added, and the mixture stirred at rt overnight. Analysis by HPLC showed a mixture of approximately 1:3:2 starting material:product:diethylbenzimidazole. The solids were filtered off and rinsed with EtOAc (60 mL). The filtrate was washed with saturated aqueous NH4Cl (2×50 mL), H2O (2×50 mL), 1% aqueous LiOH (4×50 mL), and brine (25 mL). The solution was filtered through phase separation paper and concentrated to 1.85 g of a yellow oil. The crude oil was chromatographed on silica gel with the product eluting with 25-35% EtOAc in hexanes. The product fractions were concentrated in vacuo to a white solid that was collected with hexanes. The material was dried to give 855 mg of 70 as a white solid (38%). 1H NMR (60 MHz, CDCl3): δ 7.8-7.5 (m, 2H), 7.5-7.0 (m, 3H), 6.9-6.6 (m, 3H), 3.8 (qt, 2H), 3.3-2.9 (m, 4H), 1.3 (t, 3H) ppm. HPLC analysis (15:10:75 H2O:A1:MeOH) showed a purity of 99% with a retention time of 3.6 min.
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