Dimethylformamide → 3-(Methylthio)picolinaldehyde

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To a cold (−78° C.) stirred solution of TMEDA (0.60 mL, 4.0 mmol) in dry diethyl ether (15 mL) was added a 2.5 M solution of nBuLi in hexanes (1.6 mL, 4.0 mmol). The resulting mixture was stirred 30 min at −78° C., at which point a solution of 3-(methylthio)pyridine (prepared as described by Trecourt, F.; Breton, G.; Bonnet, V.; Mongin, F.; Marsais, F.; Queguiner, G. Tetrahedron 2000, 56, 1349–1360) (500 mg, 4.0 mmol) in dry diethyl ether (5 mL) was added dropwise. The resulting red/orange solution was stirred 2 h at −78° C., then neat DMF (0.31 mL, 4.4 mmol) was added dropwise and stirring was continued for a further 2 h. Saturated aqueous sodium bicarbonate (20 mL) was added, then the phases were separated and the aqueous layer was extracted with CH2Cl2 (3×30 mL). The combined organic extracts were dried (MgSO4), and concentrated in vacuo. Purification of the crude material thus obtained by flash chromatography (silica gel, 4:1 hexanes-EtOAc) afforded 119 mg (19%) of 3-methylsulfanyl-pyridine-2-carbaldehyde. 1H NMR (CDCl3)] 2.45 (s, 3H), 7.42 (dd, 1H, J=8, 5 Hz), 7.67 (d, 1H, J=9 Hz), 8.50–8.52 (m, 1H), 10.14 (s, 1H).

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