反应详情

A mixture of triethyl orthoacetate (25 ml), 5,5-dichloro-4-hydroxy-2-methyl-6,6,6-trifluorohex-2-ene (3.5 g), and isobutyric acid (0.11 g) was heated at the reflux temperature. The refluxing volatiles were condensed and collected in a Dean & Stark apparatus containing molecular sieves (4A) to collect the by-product ethanol and separate it from the orthoacetate which was returned to the mixture. After 30 minutes the more volatile components were removed by evaporation under reduced pressure and the residual oil (consisting principally of 5,5-dichloro-4-(1,1-diethoxyethoxy)-2-methyl-6,6,6-trifluorohex-2-ene, 3.8 g) collected. This was then heated with isobutyric acid (10 μl) at the reflux temperature for 16 hours under a condenser containing molecular sieves (4A) to remove ethanol from the condensate. The residual oil was subjected to purification by column chromatography using a 15:1 (by volume) mixture of hexane:ethyl acetate as eluant and a silica gel column (230-400 mesh, 60 Å) to obtain ethyl 6,6-dichloro-3,3-dimethyl-7,7,7-trifluorohept-4-enoate, identified by nuclear magnetic resonance, and gas chromatographic mass-spectroscopy.

1. temperaturewas heated at the reflux temperature
2. customcondensed
3. customcollected in a Dean & Stark apparatus
4. additioncontaining molecular sieves (4A)
5. customto collect the by-product ethanol
6. customseparate it from the orthoacetate which
7. customAfter 30 minutes the more volatile components were removed by evaporation under reduced pressure
8. customcollected
9. temperatureThis was then heated with isobutyric acid (10 μl) at the reflux temperature for 16 hours under a condenser
10. additioncontaining molecular sieves (4A)
11. customto remove ethanol from the condensate
12. customThe residual oil was subjected to purification by column chromatography
13. additiona 15:1 (by volume) mixture of hexane