反应详情

温度

-70 °C

Under argon, 9.60 g (39 mmol) of 5-hydroxy-7-isopropylspiro[chromen-2,1′-cyclobutan]-4(3H)-one (Example 46A) are dissolved in 400 ml of abs. dichloromethane and cooled to −70° C. At this temperature, 97.44 ml (97.44 mmol) of titanium(IV) chloride (1 M solution in dichloromethane) are added dropwise such that the temperature does not exceed −65° C. The mixture is stirred briefly at −70° C., 3.88 ml (42.87 mmol) of dichloromethyl methyl ether are then added and the mixture is subsequently warmed to 0° C. After 3 hours at this temperature, the reaction mixture is added carefully to ice-water and extracted four times with dichloromethane. The combined organic phases are washed three times with saturated sodium chloride solution, dried over magnesium sulfate, filtered and evaporated to dryness. The crude product obtained is adsorbed on silica gel and purified on a silica gel column (mobile phase: cyclohexane→cyclohexane/ethyl acetate 30:1). This gives 8.1 g (76% of theory) of the title compound in a purity of 77%.

1. customdoes not exceed −65° C
2. temperaturethe mixture is subsequently warmed to 0° C
3. extractionextracted four times with dichloromethane
4. washThe combined organic phases are washed three times with saturated sodium chloride solution
5. dry with materialdried over magnesium sulfate
6. filtrationfiltered
7. customevaporated to dryness