Photochemical Studies on Benzonorbornene Derivatives: Medium Effects and Asymmetric Induction

The photochemical behaviors of benzonorbornene derivatives were investigated in the solid state as well as in the solution. In acetonitrile solution, benzonorbornene derivatives underwent the Norrish type II reaction affording a ratio of 1:1 of cyclization and cleavage products, whereas in the solid state, the sole cyclization product was obtained. The stereochemistry of the photoproducts was identified by the X-ray crystallography. Enantiomeric excesses of up to 97% can be achieved through the use of the solid-state ionic chiral auxiliary method of asymmetric synthesis.