反应详情

温度

110 °C

365.2 g of acetic anhydride (3.54 mol) were initially charged in the stirred vessel and heated to 110° C. Within 2 hours, 356.3 g of crude ethyl 4,4-difluoroacetoacetate from synthesis example 7 (26.5% ethyl 4,4-difluoroacetoacetate solution in ethanol/ethyl acetate) and 154.4 g (1.02 mol) of triethyl orthoformate were metered in in parallel. After about half had been fed in, reflux set in at 106° C. At the end of the metered addition, the internal temperature was 92° C. The mixture was stirred for a further 5 hours at reflux temperature and then cooled to 25° C. At a pressure of 150 mbar, the low boilers (ethyl acetate, acetic acid, acetic anhydride, triethyl orthoformate) were distilled off at internal temperature from 40-90° C. To complete the removal, the pressure is lowered to 5 mbar at 90° C., and the distillation bottoms are then stirred at 95° C./5 mbar for 1 hour. The resulting distillation residue (127.5 g) comprised 90.7% by weight of the desired ethyl 2-ethoxymethylene-4,4-difluoro-3-oxobutyrate. This corresponds to an overall yield over the two synthesis stages of 86.6% (based on the ethyl difluoroacetate used in working example 7).

1. temperaturereflux
2. customset in at 106° C
3. additionAt the end of the metered addition
4. customwas 92° C
5. temperatureat reflux temperature
6. temperaturecooled to 25° C
7. distillationAt a pressure of 150 mbar, the low boilers (ethyl acetate, acetic acid, acetic anhydride, triethyl orthoformate) were distilled off at internal temperature from 40-90° C
8. customthe removal
9. customis lowered to 5 mbar at 90° C.
10. distillationthe distillation
11. stirringbottoms are then stirred at 95° C./5 mbar for 1 hour
12. distillationThe resulting distillation residue (127.5 g)
13. customThis corresponds to an overall yield over the two synthesis stages of 86.6% (