反应详情

温度

-20 °C

Benzene (200 mL) was added to compound 5b (6.69 g, 17.6 mmol), and 2,6-diisopropylaniline (3.12 g, 17.6 mmol), and p-toluenesulfonic acid monohydrate (5 mg) in a 500 mL round-bottomed flask fitted with a Dean-Stark trap. The mixture was heated to reflux under nitrogen. After 2 hours, 1H NMR spectroscopy of an aliquot indicated that the reaction had proceeded to around 90% completion. All but about 50 mL of the benzene was removed by distillation and toluene (200 mL) was added. The mixture was heated to reflux and most of the toluene was removed by distillation. Drying of the residue under reduced pressure afforded a dirty yellow solid. Dissolution of the solid in warm Et2O, followed by filtration and cooling to −20° C. afforded 6b as nice yellow crystals. Yield from two crops: 6.5 g, 69%. 1H NMR (500 MHz, CD2Cl2): 8.36 (d, 1H), 8.33 (s, 1H), 7.97 (t, 1H), 7.93 (d, 2H), 7.59 (d, 1H), 7.39-7.51 (m, 4H), 7.17 (d, 2H), 7.10 (m, 1H), 6.72 (s, 2H), 4.01 (br d, 1H), 3.92 (d, 1H), 3.39 (br, 1H), 3.03 (sept, 2H), 2.18 (s, 3H), 2.03 (s, 6H), 1.18 (d, 12H).

1. customfitted with a Dean-Stark trap
2. temperatureThe mixture was heated
3. temperatureto reflux under nitrogen
4. customAll but about 50 mL of the benzene was removed by distillation and toluene (200 mL)
5. additionwas added
6. temperatureThe mixture was heated
7. temperatureto reflux and most of the toluene
8. customwas removed by distillation
9. customDrying of the residue under reduced pressure
10. customafforded a dirty yellow solid
11. filtrationfollowed by filtration