Reaction Steps
To a solution of 4-methoxy-3-(3,5,5,8,7-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl) benzyl alcohol (195 mg, 0.57 mmol) in acetic acid (glacial, 3 mL) was added HBr (48%, 1 mL) and the resulting mixture heated at reflux for 2 hours. The solution was cooled to room temperature, diluted with ethyl acetate and washed successively with water and brine, dried over anhydrous magnesium sulfate, filtered and evaporated to afford 200 mg of crude 4-methoxy-3-(3,5,5,8,7-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl) benzyl bromide. To a stirred solution of 2,4-thiazolidinedione (133 mg, 1.14 mmol) in anhydrous THF (6 mL) was added, at −78° C. under argon, n-BuLi (1.6M in hexane, 1.5 mL, 2.4 mmol) dropwise. The mixture was maintained at −78° C. for 15 minutes and then warmed to 0° C. for 30 minutes to complete the dianion formation. Upon recooling to −78° C., 4-methoxy-3-(3,5,5,8,7-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl) benzyl bromide was added in THF (3 mL). After 30 minutes the orange solution was allowed to warm to room temperature. After 1.5 hours, the solution was treated with 2N HCl, diluted with ethyl acetate and washed successively with water and brine, dried over anhydrous magnesium sulfate, filtered and evaporated. The residue was chromatographed on silica gel (eluent: ethyl acetate/hexane 2:8) to give 61 mg of 5-[4-methoxy-3-(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydronaphthalen-2-yl)benzyl] thiazolidine-2,4-dione (24% for 3 steps from benzaldehyde). 1H NMR (500 MHz; CDCl3): δ1.27 (s, 6 H); 1.26 (s, 6 H); 1.69 (s, 4 H); 2.08 (s, 3 H); 3.12 (dd, J1=14.0 Hz, J2=9.5 Hz, 1 H); 3.50 (dd, J1=14.0 Hz, J2=4.0 Hz, 1 H); 3.76 (s, 3 H); 4.54 (dd, J1=9.5 Hz, J2=4.0 Hz, 1 H); 6.89 (d, J=8.0 Hz, 1 H); 7.03 (d, J=2 Hz, 1 H); 7.07 (s, 1 H); 7.14 (s, 1 H); 7.17 (dd, J1=8.0 Hz, J2=2.0 Hz, 1 H), 7.95 (br, 1 H).
