Novas evidencias da competição fotoquímica entre os rearranjos di-π-metano e π-metano

Abstract

The photochemistry of some substances related to 1,1-dicyano-3-phenylpropene is discussed. The focus of attention is the di-π-methane rearrangement and the occurrence of competition between this and cyclopropane formation by hydrogen migration followed by cyclization (π-methane rearrangement). The main conclusion is that factors such as the increase in solvent polarity and the presence of electro-donating substituents in the aromatic ring (or naphthyl as aryl group), which decrease the efficiency of the di-π-methane rearrangement, do not seem to affect the π-methane rearrangement to the same extent. A possible interpretation is that two different non-equilibrium conformations of the excited state are involved.