854.6 mg (6.733 mmol) of oxalyl chloride in 14.5 ml of dichloromethane is introduced into a heated flask. At −70° C., 1.05 ml of DMSO, dissolved in 3 ml of dichloromethane, is added in drops, and the batch is stirred for five more minutes. Then, 2 g (6.12 mmol) of 4-(4-chloro-2-methoxyphenyl)-2-hydroxy-4-methyl-2-trifluoromethyl-pentan-1-ol, dissolved in six milliliters of dichloromethane, is added in drops. After 20 minutes of stirring, the batch is carefully mixed with 4.24 ml (30.61 mmol) of triethylamine, specifically in a temperature range of between −70 and −60° C. After five minutes of stirring at −70° C., the reaction mixture is allowed to slowly come to room temperature. 25 ml of water is added, and the batch is stirred for another hour at room temperature. After phase separation, the aqueous phase is shaken once with 100 ml of dichloromethane. The combined organic extracts are washed with 1% sulfuric acid, 5% sodium bicarbonate solution and brine. According to the conventional procedure, 1.92 g (96.9%) of the desired aldehyde is obtained, which is incorporated in crude form into the next stage.
