Acetic acid, 2-(triphenylphosphoranylidene)-, ethyl ester → (E)-5,5-bis(4-fluorophenyl)-2,4-pentadienoic acid ethyl ester

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Reaction Steps

As described in Example 99, 3.3-bis(4-fluorophenyl)-2-propenal (9.8 g) was reacted with (carbethoxymethylene)triphenylphosphorane (14.3 g) in ethanol (20 mL) for 30 minutes at ambient temperature. The mixture of esters obtained from the usual work up was purified by HPLC (dichloromethane-hexane; 1:1) to give 2.0 g of the less polar (Z)-5,5-bis(4-fluorophenyl)-2,4-pentadienoic acid ethyl ester as an oil, and 9.3 g of (E)-5,5-bis(4-fluorophenyl)-2,4-pentadienoic acid ethyl ester. A sample of the (E)-isomer was crystallized from hexane to give the pure ester, mp 71°-72.5° C. Anal. Calculated for C19H16F2O2 : C, 72.60; H, 5.13; F, 12.09 Found: C, 72.56; H, 5.17; F, 12.36.

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