Thiophene-3-carboxylic acid → 2-Isonicotinoylthiophene-3-carboxylic acid

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Reaction Conditions

Reaction Steps

n-BuLi (23.2 mL, 56.2 mmol, 2.5M in THF) was added dropwise to a solution of diisopropylamine (5.2 g, 51.5 mmol) in anhydrous THF (40 mL) at −30° C. The mixture was stirred at the same temperature for 0.5 h and then cooled to −78° C. and HMPA (0.8 g, 4.7 mmol) was added slowly. Then a solution of thiophene-3-carboxylic acid (3.0 g, 23.4 mmol) in anhydrous THF (50 mL) was added slowly. The mixture was stirred at the same temperature for 1 h. Then N-methoxy-N-methyl-4-pyridinecarboxamide (5.0 g, 46.9 mmol) was added dropwise to the stirring mixture at −78° C. The reaction mixture was stirred for another 1 h at room temperature and was then quenched with H2O (10 mL). The aqueous layer was acidified with 5% aq. HCl to pH 1-2 and the resulting precipitate collected by filtration. The filter cake was washed with DCM and the filtrate was extracted with DCM (3×200 mL). The organic layers were dried over Na2SO4 and concentrated under reduced pressure. The crude product was washed with DCM to give the title product (2.2 g, 40% yield) as a white solid. LC-MS (Method A): m/z 234 (M+H)+, Rt: 0.57 min.

Provenance & Evidence