Synthesis
The general procedure for the synthesis of 3-iodo-4-methoxypyridine from 4-methoxypyridine was as follows: n-butyllithium (ca. 1.6 M hexane solution, 1.5 mmol) was sequentially added to a stirred solution of 2,2,6,6-tetramethylpiperidine (0.25 mL, 1.5 mmol) in tetrahydrofuran (THF, 2-3 mL) at 0 °C. After 5 min, n-butyllithium (ca. 1.6 M hexane solution, 1.5 mmol) was added. ZnCl2TMEDA complex (0.13 g, 0.50 mmol). The reaction mixture was continued to be stirred at 0 °C for 15 min and then 4-methoxypyridine (1.0 mmol) was added at 0-10 °C. After the reaction mixture was stirred for 2 h at room temperature, a THF (4 mL) solution of iodine (I2, 0.38 g, 1.5 mmol) was added. After the mixture was stirred overnight, the reaction was quenched by the addition of saturated aqueous sodium thiosulfate (Na2S2O3) solution (4 mL) and extracted with ethyl acetate (AcOEt, 320 mL). The organic layers were combined, dried with anhydrous magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure. Finally, the target product, 3-iodo-4-methoxypyridine, was purified by silica gel column chromatography (eluent given in the product specification).
References
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[2] Tetrahedron, 1993, vol. 49, # 37, p. 8373 - 8380
[3] Tetrahedron Letters, 2011, vol. 52, # 36, p. 4590 - 4594
[4] Chemical Communications, 2014, vol. 50, # 85, p. 12859 - 12862
[5] Chemistry - A European Journal, 2013, vol. 19, # 24, p. 7944 - 7960
