Synthesis of (Z)-Cinnamate Derivatives via Visible-Light-Driven E-to-Z Isomerization

(Z)-Cinnamate derivatives are prevalent in natural bioactive products and in organic synthesis. Herein, we report a practical approach toward the efficient synthesis of ( Z )-cinnamate derivatives via visible-light-driven isomerization. When E -isomers of cinnamate derivatives were irradiated with blue light in the presence of 1 mol% Ir (2) (ppy) (4) Cl (2) (ppy = 2-phenylpyridine), Z -isomers were readily obtained in good yields. This strategy allows the large-scale synthesis of ( Z )-cinnamate derivatives with simple purification. This convenient, mild, and green synthetic methodology was subsequently applied to the synthesis of coumarins.