Hydrochloric Acid → 4-(5-Amino-1-methyl-1H-benzoimidazol-2-yl)-butyric acid methyl ester hydrochloride

Participants

Reaction Steps

A one liter Buchi reactor was charged with 42.7 g (131.4 mmol, 1.0 equiv.) of 4-[(2,4-dinitro-phenyl)-methyl-carbamoyl]-butyric acid methyl ester, 20 g of 10% palladium on carbon (4.7% weight ratio palladium vs. starting material), and 650 mL of methanol at ambient temperature. The resulting mixture was subjected to hydrogenation at 40 psi overnight, about 18 hours. HPLC indicated that the reaction was complete in about 6-7 hours (HPLC Method B). The reaction mixture was filtered through a thin layer of Celite® 540. To the filtrate was added 12 mL of concentrated hydrochloric acid (1.1 equiv.). The resulting mixture was stirred under reflux for 3.5 hours. Solvent was removed under reduced pressure, and the solids were slurried in 1800 mL of 2 vol % of Methanol/Tert-butyl methyl ether at room temperature overnight. The solids were collected by filtration. The product was dried at 45-50° C. overnight under vacuum to afford a coffee-colored solid (36.8 g, 99% yield) with a purity of 99 Area % by HPLC analysis (HPLC Method B).

Provenance & Evidence