To a suspension prepared by suspending 1.52 g (38.0 mmol) of 60% sodium hydride in 15 ml of THF was added dropwise solution of 5.29 g (17.3 mmol) of the 4-(trans-4-n-pentylcyclohexyl)-phenyldithiocarboxylic acid obtained by the first step, in 20 ml of THF under a condition cooled with ice in 15 min, and stirred as it was for 30 min. To this reaction solution was added dropwise solution of 2.50 g (14.4 mmol) of 2,3-difluoro-4-ethoxyphenol in 20 ml of THF in 15 min and stirred as it was for 30 min. To this reaction solution was added dropwise solution of 9.64 g (38.0 mmol) of iodine in 20 ml of THF in 15 min, stirred as it was for 1 hour, warmed up to room temperature, and then stirred at the same temperature overnight. This reaction solution was poured into 10% aqueous sodium thiosulfate solution and extracted with 100 ml of diethyl ether. The organic layer was dried over anhydrous magnesium sulfate, the solvent was distilled off under a reduced pressure, and the residue was purified by silica gel column chromatography (eluent: heptane) and further recrystallized from heptane to obtain 2.0 g of 2,3-difluoro-4-ethoxyphenyl 4-(trans-4-n-pentylcyclohexyl)thiobenzoate (yield 31.2%).
