Direct Irradiation of (E)‐Styrylpyridin‐2(1H)‐ones to (Z)‐Isomers with Visible Light

The E to Z isomerization of styrylpyridin‐2(1H)‐ones was achieved through visible light (420 nm) irradiation in dioxane at ambient temperature. Driven by the visible light, (E)‐3‐styrylpyridin‐2(1H)‐ones, (E)‐4‐styrylpyridin‐2(1H)‐ones and (E)‐5‐styrylpyridin‐2(1H)‐ones in dioxane at room temperature under Argon atmosphere were successfully converted to the corresponding (Z)‐styrylpyridin‐2(1H)‐ones in good yields. The described E to Z photoisomerization of styrylpyridin‐2(1H)‐ones proceeded smoothly with the 420 nm blue light, avoided usage of photocatalysts, additives and are easy to operate.