Lawesson's reagent → N-(3,5-difluorophenyl)-2-pyridinecarbothioamide

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Reaction Steps

N-(3,5-Difluorophenyl)-2-pyridinecarboxamide (7.00 g, 29.9 mmol) was treated with Lawesson's reagent (6.28 g, 15.5 mmol) in toluene (90 mL) at reflux temperature for 4 hours. The solvent was removed, and the residue was dissolved in dichloromethane, preadsorbed onto silica gel, and flash chromatographed (300 g of silica gel eluted with 10% ethyl acetate in petroleum ether). Recrystallization from a mixture of ethyl acetate and hexane afforded N-(3,5-difluorophenyl)-2-pyridinecarbothioamide (3.58 g, 48%) as a yellow solid, m.p. 140°-142° C. Overall yield 33%.

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