反应详情

2Chloro-1,1-difluoro-3-(p-methoxyphenyl)-2-cyclobutene (215 g., 0.93 mole) is poured gradually into 272 ml. of concentrated H2SO4 with stirring. The rate of addition is adjusted to maintain the reaction temperature below 40° C. When the reaction subsides, the cooling bath is removed, but stirring is continued for 20 min. The mixture is poured into 3 l. of water. A precipitate forms, and is collected on a filter, washed with water, and air-dried. recrystallization of this material twice from i-PrOH yields 128.8 g. (66%) of the desired intermediate, m.p. 96°-98° C. An analytical sample was prepared by chromatography an alumina (benzene) and recrystallized from heptane, m.p. 98-100° C.

1. additionThe rate of addition
2. temperatureto maintain the reaction temperature below 40° C
3. customWhen the reaction subsides
4. customthe cooling bath is removed
5. additionThe mixture is poured into 3 l
6. customA precipitate forms, and is collected on a filter
7. washwashed with water
8. customair-dried
9. customrecrystallization of this material twice from i-PrOH
10. customyields 128.8 g
11. customAn analytical sample was prepared by chromatography an alumina (benzene)
12. customrecrystallized from heptane, m.p. 98-100° C.