A mixture of (6-(tert-butoxycarbonylamino)pyridin-3-yl)methyl methanesulfonate (102; 1.30 g, 5.4 mmol), benzyl piperazine-1-carboxylate 103; (1.42 g, 6.5 mmol), K2CO3 (2.30 g, 16.1 mmol) and NaI (0.08 g, 0.54 mmol) in DMF (20 mL) was stirred at 60° C. for 2 h. The reaction mixture was filtered and the filtrate was concentrated under reduced pressure. Water (30 mL) was added and the mixture was filtered. The collected solids were washed further with water and dried to afford benzyl 4-((6-(tert-butoxycarbonylamino)pyridin-3-yl)methyl)piperazine-1-carboxylate 104 (2.20 g, 96%).
