反应详情

温度

-5 °C

1,7-Dimethyl-4,10-dioxa-tricyclo[5.2.1.0]dec-8-ene-3,5-dione 1 (30.0 g, 0.150 mol) is added slowly in portions to stirred 98% sulfuric acid (300 mL) in a 1 L flange flask cooled to −5° C. using a salt-ice bath—note that the temperature is kept below 0° C. during the addition. The mixture is stirred for 30 mins at −5° C. and then allowed to warm up to 22° C. The mixture is carefully poured onto crushed ice (1.5 L). The cream precipitate that formed is filtered off and washed with ice water. The precipitate is dissolved in a 5% aq. sodium hydroxide solution (225 mL) with stirring. Glacial acetic acid (20 mL) is added slowly to the stirred solution. A cream precipitate forms and this is filtered off and discarded. 37% Hydrochloric acid (50 mL) is added to the stirred filtrate and the mixture is stirred for 2 h during which time a precipitate is formed. The precipitate is filtered off and dried in the vacuum oven overnight to yield the product as a cream solid (11.13 g, 41%). The filtrate is allowed to stand overnight during which time further product precipitated out. The second crop of precipitate is filtered off and dried under vacuum to yield the product 2 as a cream solid (5.79 g, 21%): 1H-NMR (300 MHz, CDCl3) δ 7.18 (s, 2H), 2.40 (s, 6H).

1. additionis kept below 0° C. during the addition
2. temperatureto warm up to 22° C
3. additionThe mixture is carefully poured
4. customThe cream precipitate that formed
5. filtrationis filtered off
6. washwashed with ice water
7. dissolutionThe precipitate is dissolved in a 5% aq. sodium hydroxide solution (225 mL)
8. stirringwith stirring
9. additionGlacial acetic acid (20 mL) is added slowly to the stirred solution
10. filtrationA cream precipitate forms and this is filtered off
11. addition37% Hydrochloric acid (50 mL) is added to the stirred filtrate
12. stirringthe mixture is stirred for 2 h during which time a precipitate
13. customis formed
14. filtrationThe precipitate is filtered off
15. customdried in the vacuum oven overnight