General procedure for the synthesis of 5-formyl-3-pyridinecarbonitrile from 5-(hydroxymethyl)nicotinonitrile:
(d) 5-(hydroxymethyl)nicotinonitrile (0.070 g, 0.52 mmol), anhydrous dichloromethane (1.04 mL), and manganese oxide (0.181 g, 2.09 mmol) were mixed to form a black suspension, which was heated to reflux and the progress of the reaction was monitored by thin-layer chromatography (TLC). after 8 h, the reaction mixture was cooled to room temperature, and to a reaction flask additional manganese oxide (0.095 g, 1.1 mmol). Subsequently, the reaction mixture was heated to reflux again.After 18 h, the reaction was still incomplete, so manganese oxide (0.097 g, 1.1 mmol) was added again. After continued heating at 60 °C for 72 h, the reaction mixture was cooled to room temperature, diluted with ethyl acetate (50 mL), filtered through diatomaceous earth and washed with additional ethyl acetate (50 mL). The organic filtrates were combined, dried with magnesium sulfate, filtered through sintered glass and concentrated to give 0.064 g (93% yield) of white solid product. Further purification by column chromatography (eluent: ethyl acetate/hexane, 1:3) afforded 0.038 g (55% yield) of 5-formyl-3-pyridinecarbonitrile as a white solid.
1H NMR (CDCl3) data: δ 10.17 (s, 1H), 9.28 (d, J = 1.9 Hz, 1H), 9.11 (d, J = 2.2 Hz, 1H), 8.45 (dd, J = 2.2, 1.9 Hz, 1H).
