Visible-light sensitization-promoted isomerization of cinnamamides

Cinnamamide is a class of compounds with a styrene structure, and the steric configuration (Z/E configuration) has a significant impact on its physical, chemical, and biological properties. Cinnamamides, both naturally extracted and synthesized, are typically trans-isomer. As the synthesis of cis-isomer is more difficult than that of the trans-isomer, the configurational isomerization reaction of cinnamamide under the promotion of visible light is primarily investigated in this paper. A simple and efficient method of cinnamamide E to Z isomerization has been established by optimising the reaction conditions. With only 0.01 mol% of the organic photosensitizer 4CzIPN, the unprotected E cinnamamide can be successfully converted into the Z configuration with the high yield of 99% and Z/E ratio of 95:5. This reaction has the advantages of mild conditions, less catalyst dosage, and good functional group tolerance.