0.7 Gram (1.9 mmol) of the 4,4,5,8-tetramethyl-6-(1-ethyl-5-hydroxypyrazol-4-yl)carbonylthiochroman-1,1-dioxide (Compound Ic-1) corresponding to pyrazole derivative (I-H), obtained in Referential Production Example 5, was dissolved in 8 ml of methylene chloride. Then, a solution of 0.51 g (3.8 mmol) of potassium carbonate in 5 ml of water was added, and further, 0.49 g (3.8 mmol) of ethanesulfonyl chloride and 0.05 g (0.2 mmol) of benzyltriethylammonium chloride, corresponding to compound B-A-Hal, were added. The mixture was allowed to react at room temperature for 2 hours, and further refluxed under heat for 2 hours. The reaction mixture was allowed to cool, and then a methylene chloride layer was recovered and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the resultant oil was purified by silica gel column chromatography to give 0.73 g (yield 82%) of 4,4,5,8-tetramethyl-6-(1-ethyl-5-ethanesulfonyloxypyrazol-4-yl)carbonylthiochroman-1,1-dioxide (Compound Ic-2).
