Citric Acid → N-Butyloxycarbonyl-3-(3-pyrrolidine-2-one-1-ylmethylphenyl)-5-iso-butyl-thiophene-2-sulfonamide

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Reaction Steps

To a solution of 3-(3-pyrrolidine-2-one-1-ylmethylphenyl)-5-iso-butyl-N-tert-butylthiophene-2-sulfonamide (66.7 mg, 0.149 mmol; see step (a)) in CH2Cl2 (2 mL) was added BCl3 (0.6 mL, 1.0 M in hexane) and the reaction mixture was stirred for 1 h at ambient temperature. The reaction mixture was concentrated in vacuo. Water (5 mL) was added to the residue and this was then extracted with EtOAc. The combined organic phase was washed with water and brine, dried (over anhydrous MgSO4) and concentrated in vacuo. To the crude product dissolved in pyridine (1.5 mL) was added pyrrolidinopyridine (44.1 mg, 0.297 mmol) and butyl chloroformate (189.1 μL, 1.49 mmol) and the reaction mixture was stirred overnight. Citric acid (3 mL, 10% aq) was added to the reaction mixture, which was then extracted with EtOAc, dried (over anhydrous MgSO4), concentrated in vacuo, and the residue purified by LCMS (20-100% CH3CN in water) to give the title compound in 74% yield, over two steps, (54 mg, 0.110 mmol).

Provenance & Evidence