P-Unsaturated Acids and Esters

The C-C double bonds conjugated with carboxyl functions are usually much more readily hydrogenated than usual olefinic bonds, especially with nickel and palladium catalysts. Ethyl cinnamate is rapidly hydrogenated over Raney Ni under mild conditions (eq. 3.19).115 It is also hydrogenated over palladium oxide much faster (eq. 3.20) than over platinum oxide with which 2.9 h were required under the same conditions.5 Cinnamic acid was hydrogenated smoothly to dihydocinnamic acid as the sodium salt over Urushibara Ni in water under ordinary conditions (eq. 3.21).116 

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Conjugate additions of dialkylcuprates to (3-substituted-a,P-unsaturated acids and esters give low yields. Addition of boron trifluoride etherate, BFj-OEtj, to certain dialkylcuprates and higher-order cuprates enhances their reactivity in Michael additions to conjugated acids and esters. 

Itoh, M., Tokuda, M., Hataya, M., and Suzuki, A., Photochemical reaction of a,P-unsaturated acids and esters, Hokkaido Daigaku Kogakubu Kenkyu Kokoku, 60, 37,1971. 

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