Photo-induced transformations. Part 76. Ring expansion through a [2 + 2] photocycloaddition-β-scission sequence; the photorearrangement of endo-4-cyanotricyclo[6.4.0.0]dodeca-1(12),6,8,10-tetraen-5-yl hypoiodite to 4-cyanotricyclo[6.4.0.0]dodeca-1 (12),6,8,10-tetraen-5-one. X-Ray crystal structure of 4-cyanotricyclo[6.4.0.0]dodeca-1(12),6,8,10-tetraen-5-one

The irradiation of endo-4-cyanotricyclo[6.4.0.02.5]dodeca-1 (12),6,8,10-tetraen-5-ol (1), derived from the [2 + 2] photocycloaddition of 2-naphthol with acrylonitrile, in the presence of HgO–I2 in benzene, gives 4-cyanotricyclo[6.4.0.02.4]dodeca-1(12),6,8,10-tetraen-5-one (2) in 40% yield. The unique molecular structure of product (2), which has the flattened boat conformation of a seven-membered ring, was determined by means of X-ray crystallographic analysis