[Se](=O)=[O:2].[CH3:4][C:5]([O:14][C:15](=[O:17])[CH3:16])([C:7]1[C:8]([CH3:13])=[N:9][CH:10]=[CH:11][CH:12]=1)[CH3:6]>O.O1CCOCC1>[CH:13]([C:8]1[C:7]([C:5]([O:14][C:15](=[O:17])[CH3:16])([CH3:4])[CH3:6])=[CH:12][CH:11]=[CH:10][N:9]=1)=[O:2]Selenium dioxide (1.44 g, 13.0 mmol) was added to a solution of acetic acid 1-methyl-1-(2-methyl-pyridin-3-yl)-ethyl ester (1.25 g, 6.48 mmol) dissolved in a mixture of water (2.5 mL) and 1,4-dioxane (25 mL). The resulting mixture was stirred at 100° C. for 60 hours. The solvent was removed under reduced pressure and the brown oil was quenched with saturated NaHCO3 (30 mL) and extracted with CH2Cl2 (5×50 mL). The combined organic extracts were dried (Na2SO4), filtered, and concentrated in vacuo to afford a brown oil. Purification via column chromatography on silica gel (hexanes:EtOAc, 1:1, v/v) afforded acetic acid 1-(2-formyl-pyridin-3-yl)-1-methyl-ethyl ester as a yellow oil (0.62 g, 46%). 1H NMR (CDCl3) δ 1.91 (s, 6H), 2.03 (s, 3H), 7.48 (dd, 1H, J=9.0, 6.0 Hz), 7.83 (dd, 1H, J=9.0, 3.0 Hz), 8.69 (dd, 1H, J=6.0, 3.0 Hz), 10.49 (s, 1H).
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