tert-Butyl 2-(4-(pyridin-2-yl)benzyl)hydrazinecarboxylate

White Solid

An intermediate for the preparation of antiviral protease inhibitors.

Step 1: A mixture of 4-(pyridin-2-yl)benzaldehyde X (17.7 g, 96.6 mmol) and tert-butylcarbamate (12.2 g, 92.3 mmol) in ethanol (125 mL) was kept at reflux under nitrogen for 4 hours (h). The reaction mixture was cooled to 40 C and ice (60 g) was added. The resulting mixture was stirred for 20 minutes (min). The precipitate was collected by filtration, washed with water and dried in a vacuum oven (60 C). Product XII, yield 25.0 g, 91%.

Step 2: A solution of the above product (23.15 g, 77.85 mmol) in methanol (350 ml) was treated with 20% palladium activated charcoal (2.3 g, 50% wet) and hydrogenated at 10 psi for 4 hours. The reaction mixture was filtered through diatomaceous earth and the filter cake was washed with methanol and the solvent was removed in a rotary evaporator. The residue was recrystallized with heptane and dried in a vacuum oven (40 C). The product 2-[4-(2-pyridinyl)benzyl]-hydrazinecarboxylic acid tert-butyl ester was obtained in a yield of 2.48 g, 97%.