198904-84-6

24424-99-5

198904-84-6

General procedure for the synthesis of tert-butyl [[4-(2-pyridinyl)phenyl]methylene]-hydrazine carboxylate from di-tert-butyl dicarbonate: 4-(pyridin-2-yl)benzaldehyde hydrazone (2.2 g, 12.0 mmol), THF (50 mL), and a 0.5 M aqueous sodium hydroxide solution (10 mL) were added to a 100 mL four-necked flask, followed by a 20-minute period at 30 °C under stirring. A solution of di-tert-butyl dicarbonate (5.2 g, 23.8 mmol) in THF (5 mL) was added dropwise. The reaction mixture was heated to 55-60 °C and stirred vigorously for 3 h at this temperature. The reaction progress was monitored by HPLC and the yield of N-(tert-butoxycarbonyl)-N'-[4-(pyridin-2-yl)phenylmethylene]hydrazine was confirmed to be 93.2%. After completion of the reaction, the mixture was concentrated under reduced pressure and the resulting crystalline residue was washed with a small amount of cold methanol and recrystallized from toluene to give purified N-(tert-butoxycarbonyl)-N'-[4-(pyridin-2-yl)phenylmethylene]hydrazine (yield 2.1 g). The product was characterized by the following data: melting point: 169.2-171.5 °C; IR (KBr, cm-1): 3308, 1712, 1612, 1586, 1528, 1510, 1468, 1434, 1394, 1360, 1310, 1246, 1158, 780; 1H-NMR (CDCl3, ppm) δ: 1.55 (s, 9H), 7.24 (m, 1H), 7.75 (m, 2H), 7.78 (d, 2H), 7.87 (s, 1H), 8.00 (d, 2H), 8.16 (s, 1H), 8.70 (m, 1H).