反应详情

3-(2-Ethylhexyl)-thiophene (19.6 g, 100 mmol) and anhydrous tetrahydrofuran (250 mL) were charge into a 500 ml flask. The solution was cooled to −78° C. with dry ice/acetone. N-butyl lithium (40 mL, 2.5 M in hexane, 100 mmol) was dropped into the solution. After addition, the reaction solution was warmed to room temperature and stirred for 30 min. Then, the solution was cooled to −78° C. again and 1-formylpiperidine (13.6 g, 120 mmol) was added in one shot. The reaction solution was allowed to warm slowly to room temperature and stirred at room temperature for overnight. The solution was acidified with hydrochloric acid (2 N) and then extracted with ether (2×100 mL). The organic extracts were combined and washed with distilled water (2×100 mL), dried over anhydrous magnesium sulfate and rotary evaporated to remove the solvent. The residue was run through a silica-gel column using ethyl acetate/hexanes (1/10, v/v, Rf=0.3) as the eluent to give a colorless liquid product (18.4 g, 78% yield). 1H NMR (400 MHz, CDCl3) δ (ppm): 9.86 (s, 1H), 7.56 (s, 1H), 7.34 (s, 1H), 2.59 (d, 2H, J=6.8 Hz), 1.58 (m, 1H). 1.18-1.34 (m, 8H), 0.84 (t, 6H, J=7.2 Hz); (Note: contain about 5% of 3-substituted isomer).

1. additionAfter addition
2. temperatureThen, the solution was cooled to −78° C. again
3. temperatureto warm slowly to room temperature
4. stirringstirred at room temperature for overnight
5. extractionextracted with ether (2×100 mL)
6. washwashed with distilled water (2×100 mL)
7. dry with materialdried over anhydrous magnesium sulfate
8. customrotary evaporated
9. customto remove the solvent