3-[3-(4-Methyl-benzo[b]thiophen-3-ylmethyl)-2-oxo-2,3-dihydro-benzimidazol-1-yl]-propionitrile (58 mg, 0.17 mmol), azidotrimethylsilane (0.047 mL, 0.33 mmol) and dibutyltin oxide (4.2 mg, 0.017 mmol) are dissolved in dry DMF (2.0 mL) in microwave vial. It is then heated at 150° C. for 2 hrs in microwave reactor. Then another 0.05 mL of azidotrimethylsilane and 4.0 mg of dibutyltin oxide are added and the mixture is heated for another 2 hr at 150° C. in microwave reactor. Then water (2 mL) is added and the mixture is extracted with EtOAc (2×30 mL). The organic layers are combined and extracted with 2.0M NaOH (2×30 mL). The NaOH layers are combined and washed with EtOAc (30 mL). Then the NaOH layers are acidified with 1.0M HCl to pH=3 and it is then extracted with EtOAc (2×30 mL). All the organic layers are combined, dried (MgSO4) and concentrated to give crude product. Purification by preparative TLC using 3% MeOH in CH2Cl2 affords 15 mg (65%) of 1-(4-Methyl-benzo[b]thiophen-3-ylmethyl)-3-[2-(1H-tetrazol-5-yl)-ethyl]-1,3-dihydro-benzimidazol-2-one. LCMS (ESMS): m/z 391.07 (M+H+).
