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

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Reaction Steps

A mixture of 3,3-bis(4-methoxyphenyl)-2-propenal (22.7 g) and (carbethoxymethylene)triphenylphosphorane (30 g) in carbon tetrachloride (200 mL) was stirred overnight at room temperature and then at reflux for 5 hours to complete the reaction. The crude product (28.4 g) obtained from the usual work up consisted mainly of (E)-5,5-bis(4-methoxyphenyl)-2,4-pentadienoic acid ethyl ester. The crude ester (28.4 g) in a mixture of methanol (200 mL) and 2N sodium hydroxide solution (100 mL) was heated at reflux for 30 minutes, then most of the methanol was distilled from the reaction. The base mixture was cooled, diluted with water (300 mL), extracted with dichloromethane (3×400 mL) and then was poured into a stirred mixture of concentrated hydrochloric acid (50 mL), water (200 mL) and ice (200 mL). The yellow precipitate was filtered off, washed with water and dried. The material was triturated with ether (3×100 ml) to provide 21.5 g of (E)-5,5-bis(4-methoxyphenyl)-2,4-pentadienoic acid, mp 187°-189° C. Crystallization from dichloromethane-hexane furnished the pure acid, mp 189.5°-190.5° C.

Provenance & Evidence