tetrafluoroborate-sensitized photoreaction of 1b, the corresponding difluorosilane and anthracene were obtained in good yields. The structural and electronic features of radical cation 1a+• were provided by semiemperical molecular orbital calculation. In addition, the structure of 1a in crystals was determined by X-ray crystallography and compared with that obtained by the calculation.
Irradiation of silanorbornadienes 1 using 9,10-dicyanoanthracene as a sensitizer afforded two isomers 2 and 3 accompanied with anthracene. In the presence of molecular oxygen, dioxide 5 was obtained as an additional product These reactions are explained in terms of the initial electron donor-acceptor interaction followed by skeletal rearrangement.