Visible-light sensitization-promoted isomerization of cinnamamides

Abstract

<p indent="0mm">Cinnamamide is a class of compounds with a styrene structure, and the steric configuration (<italic>Z</italic>/<italic>E</italic> configuration) has a significant impact on its physical, chemical, and biological properties. Cinnamamides, both naturally extracted and synthesized, are typically <italic>trans</italic>-isomer. As the synthesis of<italic> cis</italic>-isomer is more difficult than that of the <italic>trans</italic>-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 <italic>E</italic> to <italic>Z</italic> isomerization has been established by optimising the reaction conditions. With only 0.01 mol% of the organic photosensitizer 4CzIPN, the unprotected <italic>E</italic> cinnamamide can be successfully converted into the <italic>Z</italic> configuration with the high yield of 99% and <italic>Z</italic>/<italic>E</italic> ratio of 95:5. This reaction has the advantages of mild conditions, less catalyst dosage, and good functional group tolerance.