Probing the Visible Light‐Driven Geometrical Isomerization of 4‐Arylbut‐3‐ene‐2‐amines

A series of thirteen 4‐arylbut‐3‐ene‐2‐amines were prepared and subjected to photosensitization experiments to interrogate their photostationary state (PS) composition of geometrical olefin isomers (E and Z). The amine PS compositions were found to depend on arene structure and temperature, while being largely independent of nitrogen substitution, solvent, or presence of triplet‐quenching oxygen. Photonic efficiency of isomerization (ζp) was found to depend on amine structure, solvent choice, and presence of quencher. With the proper choice of conditions, ζp was able to closely approach the theoretical maximum value of 0.5. Instantiated with a set of styrylamines, parameters affecting photosensitized alkene geometrical isomerization were investigated. Raised temperature was found to reduce inherent Z‐enrichment, bulky arenes reinforced Z‐enrichment, and certain heterocycles favored accumulation of E isomer. Actinometric assessment was made on the influence of arene bulk, solvent, and presence of oxygen on the reaction rate.