A mixture of 6-[3-(1-adamantyl)-4-methoxyphenyl]-2-bromonaphthalene (50 mg, 0.11 mmol), THF (1 ml) was introduced into a Schlenk tube and was heated until its complete dissolution. Next, NaH (4.5 mg, 60% dispersion in mineral oil, 0.11 mmol) was added under argon atmosphere and at room temperature, and the mixture was stirred for 10 minutes. The solution was cooled to −40° C. and n-BuLi (139.5 μl, 1.6 M in hexane, 0.22 mmol) was added, dropwise, during 30 minutes. At the same temperature, a continuous mild flow of CO2 (anhydrous gas) was introduced in the reaction for 1 h. After bringing the reaction to room temperature during 30 minutes with continuous flow of CO2, the mixture was diluted with aq HCl (5 ml, 2 M) and was vigorously stirred for 10 minutes. The resulting mixture was extracted with CHCl3 (3×5 ml) and the joined organic phases were dried with Na2SO4 and next were evaporated to dryness, giving the crude of Adapalene. The crude was purified in the same way as that of the Example 8. 15 mg of Adapalene were obtained (30%) as a white solid.
