Triethyloxonium tetrafluoroborate → Acetic acid 2-((S)-1-tert-butoxycarbonylaminoethyl)-5-fluoro-3-phenyl-3H-benzoimidazol-4-ylmethyl ester

Participants

Reaction Steps

To a suspension of ((S)-1-carbamoylethyl)carbamic acid tert-butyl ester 3.94 g, 20.9 mmol) in DCM (20 mL) was added triethyloxonium tetrafluoroborate (3.35 g, 17.6 mmol) and the reaction mixture stirred at RT for 2 hours, during which the solids dissolved. The reaction mixture was concentrated in vacuo and the residue dissolved in ethanol (20 mL). Acetic acid 3-amino-6-fluoro-2-phenylaminobenzyl ester (2.3 g, 8.38 mmol) was added and the reaction heated at 75° C. for 1 h. The reaction mixture was concentrated in vacuo, the residue dissolved in water and the product extracted with EtOAc (3×20 mL). The combined organic extracts were washed with brine, dried (MgSO4) and concentrated in vacuo. The resultant residue was subjected to flash chromatography (SiO2, eluting with 0-100% EtOAc in cyclohexane) to give the title compound as an off white solid. LCMS (Method C): RT=3.37 min, [M+H-tBu]+=372, 100%, [M+H]+=428, 40%.

Provenance & Evidence