反应详情

To a three-necked round-bottomed flask, equipped with a Dean-Stark trap (20 mL), a reflux condenser, a thermometer and a magnetic stir bar, was placed diol 1 (14.8 g, 115.5 mmol) and 370 mL of toluene under an atmosphere of N2. The mixture was brought to reflux and maintained at reflux temperature for 2 hours to azeotropically remove any moisture. About 100 mL (5×20 mL) of azeotropic mixture was collected in the Dean-Stark trap. The mixture was then allowed to slowly cool to room temperature and 0.2 g of anhydrous para-toluenesulfonic acid (PTSA) was added, followed by dropwise addition of tetraethylorthocarbonate (TEOC, 4563-91-2, 99.1%, 12.2 mL, 57.8 mmol). The resulting mixture was brought to reflux to azeotropically remove ethanol generated during this reaction. The azeotropic mixture was shaken with sale water to determine the amount (volume) of ethanol collected. After a total of 140 mL of azeotropic mixture (12.5 mL of ethanol) was collected, the reaction mixture was allowed to reflux for an additional 2 hours and then allowed to stir at 102° C. overnight. The reaction mixture was allowed to slowly cool to room temperature and then neutralized by the addition of 1 mL of triethylamine. The resulting mixture was allowed to stir at room temperature for an additional 30 min, and was stripped off solvents to give an off white solid. The crude material was then purified by flash chromatography (silica gel, CH2Cl2/hexanes 2/1 v/v) or by recrystallization from refluxing toluene. The desired product 7,9,17,18-tetroaxatrispiro[4.2.2.4.2.2]nonadeca-2,13-diene (DCP 3) was obtained as white crystals in 62% yield. Mp (DSC) 174.53° C.; 1H-NMR (CDCl3, 300 MHz) δ 5.61 (s, 2H), 3.82 (s, 4H), 2.29 (s, 4H); 13C-NMR (CDCl3, 300 MHz) δ 28.53, 114.14, 71.07, 39.79; FT-IR (CH2Cl2) (cm−1) 3052, 2947, 2928, 2880, 2842, 1614, 1481, 1267, 1210, 1171, 1014, 990, 738, 671; Anal. Calcd for C15H20O4: C, 68.16; H, 763; Found: C, 68.18; H, 7.81.

1. customTo a three-necked round-bottomed flask, equipped with a Dean-Stark trap (20 mL), a reflux condenser
2. temperatureto reflux
3. temperaturemaintained
4. temperatureat reflux temperature for 2 hours
5. customto azeotropically remove any moisture
6. customAbout 100 mL (5×20 mL) of azeotropic mixture was collected in the Dean-Stark trap
7. addition0.2 g of anhydrous para-toluenesulfonic acid (PTSA) was added
8. customgenerated during this reaction
9. customcollected
10. customAfter a total of 140 mL of azeotropic mixture (12.5 mL of ethanol) was collected
11. temperatureto reflux for an additional 2 hours
12. temperatureto slowly cool to room temperature
13. additionneutralized by the addition of 1 mL of triethylamine
14. stirringto stir at room temperature for an additional 30 min
15. customto give an off white solid
16. customThe crude material was then purified by flash chromatography (silica gel, CH2Cl2/hexanes 2/1 v/v) or by recrystallization
17. temperaturefrom refluxing toluene