反应详情

To a solution of 4a (1.0 g, 2.62 mmol) in toluene (30 mL) at 0° C. were sequentially added DMF (0.2 mL) and oxalyl chloride (1.48 g, 11.66 mmol) dropwise. The resulting mixture was allowed to warm to room temperature and stirred for 1 h, then transferred slowly to a mixture of 5a (0.50 g, 4.30 mmol) and triethylamine (0.42 g, 4.16 mmol) in THF (30 mL) at 0° C. After the mixture was warmed and stirred at room temperature for 15 h, the reaction was quenched with water and extracted with ethyl acetate (2×30 mL). The combined extracts were washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated to give the crude residue (1.22 g), which without purification, underwent intramolecular cyclization by treatment with sodium methoxide (270 mg, 5.00 mmol) in methanol (30 mL) at 60° C. for 4 h. After the reaction was complete, the reaction mixture was concentrated and poured into ice water and the resulting mixture was extracted with ethyl acetate (2×30 mL). The combined extracts were washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated. The residue was purified by flash chromatography on silica gel with hexanes/ethyl acetate (1:1) to afford the desired product 6 (0.67 g, 55%) as a white solid. 1H NMR (400 MHz, CDCl3) δ 7.41 (d, 1H), 7.25 (d, 2H), 7.22 (dd, 1H), 7.12 (d, 1H), 7.01 (d, 2H), 3.42 (s, 3H), 2.35 (s, 3H), 1.37 (s, 6H); ESMS m/z: 461.0 (M+1).

1. customat 0° C.
2. temperatureAfter the mixture was warmed
3. stirringstirred at room temperature for 15 h
4. customthe reaction was quenched with water
5. extractionextracted with ethyl acetate (2×30 mL)
6. washThe combined extracts were washed with brine
7. dry with materialdried over anhydrous sodium sulfate
8. filtrationfiltered
9. concentrationconcentrated
10. customto give the crude residue (1.22 g), which
11. concentrationthe reaction mixture was concentrated
12. additionpoured into ice water
13. extractionthe resulting mixture was extracted with ethyl acetate (2×30 mL)
14. washThe combined extracts were washed with brine
15. dry with materialdried over anhydrous sodium sulfate
16. filtrationfiltered
17. concentrationconcentrated
18. customThe residue was purified by flash chromatography on silica gel with hexanes/ethyl acetate (1:1)