Redox-Photosensitized Reactions. 5. Redox-Photosensitized Ring Cleavage of 1,1a,2,2a-Tetrahydro-7H-cyclobutindene Derivatives: Mechanism and Structure-Reactivity Relationship

Article abstract of DOI:10.1021/ja00536a025

The mechanistic aspects of the redox-photosensitized chain cycloreversion of trans,syn-indene dimer 1 have been investigated in detail.The ? complex of 1 with the cation radical of phenanthrene (and selected other aromatic hydrocarbons) that is generated by photochemical electron transfer with p-dicyanobenzene has been shown to be a key intermediate by way of which the cycloreversion of 1 rapidly occurs without the formation of its cation radical; the rate constant for the cycloreversion has been determined to be 1*10⁹ s^-1.Redox photosensitization has been applied to the other related compounds and it has been found that the cyclobutanes which can undergo redox-photosensitized ring cleavage possess the phenyl group at C₂.The importance of through-bond interactions between the two ?-electron system is discussed.