Abstract
Triplet diphenylcarbene sterically protected by trifluoromethyl and bromo groups at ortho positions was found to be extremely stable, having a lifetime of 10 min in degassed benzene at room temperature. In order to prepare persistent triplet diphenylcarbene, diphenylcarbenes bearing aryl groups at ortho positions were generated by photolysis of the corresponding diazo compounds and were studied not only by product analysis and spectroscopic method but also by laser flash photolysis techniques. These studies showed that a lifetime of a diphenylcarbene bearing phenyl groups at the ortho positions was shorter than that of ortho-brominated diphenylcarbene due to a reaction between carbene-center and the o-phenyl group to afford fluorene derivative. In order to reduce the reactivity of the o-phenyl group, diphenylcarbenes having 3,5-bis(trifluoromethyl)phenyl or 4-biphenylyl groups were also generated.
