Lawesson's reagent → ethyl 1-[(4-carbamothioyl-1,3-thiazol-2-yl)methyl]-1H-pyrazole-4-carboxylate

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Reaction Steps

To a solution (10 mL) of the compound (524 mg, 1.87 mmol) obtained in Example 33b in toluene was added 2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide (Lawesson reagent, 756 mg, 1.87 mmol), and the mixture was heated under reflux overnight. The reaction mixture was allowed to cool to room temperature, saturated aqueous sodium hydrogen carbonate solution was added, and the mixture was stirred for 30 min, and extracted with ethyl acetate. The obtained organic layer was washed with saturated brine, and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure. The obtained crude product was purified by column chromatography (hexane-hexane/ethyl acetate=1/1) and recrystallization (ethyl acetate-hexane) to give the title compound (200 mg, 36%) as pale-yellow crystals.

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