Cl[C:2]1[N:7]=[C:6]([C:8]([O:10][CH3:11])=[O:9])[CH:5]=[CH:4][CH:3]=1.C[Si]([N-][Si](C)(C)C)(C)C.[Na+].Cl.[CH2:23]([O:27]C1N=C(C(O)=O)C=CC=1)[CH2:24][CH2:25][CH3:26].S(Cl)(Cl)=O>C(O)CCC>[CH2:23]([O:27][C:2]1[N:7]=[C:6]([C:8]([O:10][CH3:11])=[O:9])[CH:5]=[CH:4][CH:3]=1)[CH2:24][CH2:25][CH3:26]To methyl 6-chloro-pyridine-2-carboxylate (2.58 g, 15.0 mmol, obtained from Example 17(a)) was added 1-butanol (35 mL) followed by sodium bis(trimethylsilyl)amide (5.51 g, 30.1 mmol). The suspension was warmed to 130° C. for 24 h after which more sodium bis(trimethylsilyl)amide (5.51 g, 30.1 mmol) was added. After another 24 h at reflux, the solution was cooled to r.t. and was poured into 200 mL 1N HCl in an ice bath. The aqueous solution was extracted twice with ethyl acetate. The organic layers were combined, dried over sodium sulfate, filtered and concentrated in vacuo resulting in 3.79 g of crude 6-butoxy-pyridine-2-carboxylic acid. To the crude 6-butoxy-pyridine-2-carboxylic acid was added thionyl chloride (100 mL) and after 1 h the resulting solution was concentrated in vacuo. To the residue was slowly added anhydrous methanol (100 mL) and after stirring o.n., the solvents were removed in vacuo. The resulting 3.73 g of crude material was purified by silica gel column chromatography (hexanes/ethyl acetate, 8:1) resulting in 2.46 g of the title compound as a colourless oil (78% yield, 11.7 mmol).
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