Diethyl Ether → 3-Fluoro-2-pyridinecarboxaldehyde
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[F:1][C:2]1[C:3]([C:8]2NC=CN=2)=[N:4][CH:5]=[CH:6][CH:7]=1.FC1N=C(C2NC=CN=2)C=CC=1.[Li]CCCC.FC1C=NC=CC=1.C([O:39]CC)C>O.CN(C=O)C>[F:1][C:2]1[C:3]([CH:8]=[O:39])=[N:4][CH:5]=[CH:6][CH:7]=1[F:1][C:2]1[C:3]([C:8]2NC=CN=2)=[N:4][CH:5]=[CH:6][CH:7]=1.FC1N=C(C2NC=CN=2)C=CC=1.[Li]CCCC.FC1C=NC=CC=1.C([O:39]CC)C>O.CN(C=O)C>[F:1][C:2]1[C:3]([CH:8]=[O:39])=[N:4][CH:5]=[CH:6][CH:7]=1
3-Fluoro-2-(1H-imidazol-2-yl)-pyridine, which is used as a starting material (e.g., in place 6-fluoro-2-(1H-imidazol-2-yl)-pyridine in the procedure given above) in the synthesis of certain compounds is prepared as follows: n-BuLi (2.5 M in hexane, 86 mL, 1.05 eq.) is added dropwise over a 90 minute interval to a solution of 3-fluoropyridine (20 g,.0.206 mol) and N,N,N′N′-tetramethylethylenediamine (31.3 mL, 0.206 mol) in ethyl ether (350 mL) at −78° C. under nitrogen. The mixture is stirred at this temperature for an additional 3 hours. Anhydrous DMF (45 mL) is then added at the same temperature. The mixture is allowed to warm to room temperature overnight. Water (170 mL) is added and organic layer separated. The aqueous layer is extracted with ether (3×200 mL), and then with ethyl acetate (2×200 mL). The combined organic layers are dried (MgSO4) and solvent removed in vacuo. The crude is purified by column chromatography (hexane:ether 2:1) to give 3-fluoro-pyridine-2-carbaldehyde as a yellowish oil.
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