Photochemical Rearrangement of Diarylethenes: Reaction Efficiency and Substituent Effects

In recent years, great synthetic potential of the photorearrangement of diarylethenes leading to naphthalene derivatives via a cascade process of photocyclization/[1,<i>n</i>]-H shift/cycloreversion has been demonstrated. In this work, first a multifaceted study of the influence of various factors on the efficiency of the photorearrangement of diarylethenes of furanone series containing benzene and oxazole derivatives as aryl residues has been carried out. The efficiency of this phototransformation (quantum yields) and the effect of methoxy substituents in the phenyl moiety have been studied. Despite the multistage process, the quantum yields of the photorearrangement are rather high (0.34–0.49). It has been found that the efficiency of photocyclization of diarylethenes increases with the introduction of electron-donating methoxy groups in the phenyl moiety. Using the DFT calculations, we have been able to estimate in the photoinduced isomer the distance between hydrogen atom and carbon atom to which it migrates in the result of the sigmatropic shift. For all studied diarylethenes, this value was 2.67–2.73 Å, which is less than the sum of van der Waals radii of carbon and hydrogen atoms (2.9 Å)