Stereodifferentiation in the photochemical cycloreversion of diastereomeric methoxynaphthalene-oxetane dyads

Intramolecular PET cycloreversion of oxetanes 1 and 2 has been achieved in acetonitrile and chloroform as solvents. Interestingly, a higher photoreactivity has been found in acetonitrile, while a significant stereodifferentiation has been found in chloroform. This stereodifferentiation can be attributed to the folded conformation which predominates in 2, with the naphthalene ring directed toward the oxetane region, allowing for the intramolecular electron transfer. Accordingly, intramolecular fluorescence quenching is also more efficient in acetonitrile, whereas stereodifferentiation is markedly higher in chloroform. Thus, a good correlation can be established between the results from steady-state irradiations and fluorescence measurements.