反应详情

温度

-78 °C

A solution of 2,2,6-trimethyl-4H-1,3-dioxin-4-one (20 g, 141 mmol) in dry THF (400 mL) was cooled to −78° C. To this solution was slowly added a LiHMDS (1M-THF, 160 mL, 160 mmol). The resulting solution was maintained at −78° C. with stirring for 30 min. To the reaction mixture was added acetoxy acetylchloride (17 mL, 160 mmol) and the resulting mixture was maintained at −78° C. for at 1 h. The reaction was then allowed to slowly warm to rt and stir for an additional 1 h. The reaction was then quenched with addition of a 1N solution of ammonium chloride. The layers were separated and the aqueous layer was extracted with ethyl acetate (5×). The organics were combined, dried, and concentrated in vacuo. The crude product was purified using a medium pressure liquid chromatography biotage system. Elution with hexanes-ethyl acetate (3:1) gave 13.1 g (38%) of a red-brown oil. The product looks clean by NMR. 1H NMR (300 MHz, CDCl3) δ 5.42 (s, 1H), 4.75 (s, 2H), 3.41 (s, 2H), 2.22 (s, 3H), 1.75 (s, 6H).

1. temperaturethe resulting mixture was maintained at −78° C. for at 1 h
2. temperatureto slowly warm to rt
3. stirringstir for an additional 1 h
4. customThe reaction was then quenched with addition of a 1N solution of ammonium chloride
5. customThe layers were separated
6. extractionthe aqueous layer was extracted with ethyl acetate (5×)
7. customdried
8. concentrationconcentrated in vacuo
9. customThe crude product was purified
10. washElution with hexanes-ethyl acetate (3:1)