The Photocycloaddition of N-Vinylcarbazole with 3-Cyanostyrene

Article abstract of DOI:10.1246/bcsj.60.2899

The photocycloaddition reaction of N-vinylcarbazole (VCZ) as an electron donor, with 3-cyanostyrene as an electron acceptor, was studied.In nonpolar solvents, two cyclobutanes of cis-1-(9-carbazolyl)-2-(3-cyanophenyl)cyclobutane and trans-1-(9-carbazolyl)-2-(3-cyanophenyl)cyclobutane (in a ratio of 3:1) were obtained from an exciplex intermediate.The structure of cis cyclobutane seemed to originate from a sandwich conformation of the exciplex.In polar solvents, a photodissociation to free ion radicals was observed and trans-1,2-di(9-carbazolyl)cyclobutane was produced efficiently by means of a chain mechanism via a cation radical of VCZ.Transient intermediates were measured by means of nanosecond laser photolysis; the results supported the reaction scheme.