ω-Isobutyryl-ω-methyl-2,3-benzocycloalk-2-en-l-ones. (6a-c) undergo both type I and typeII photoreactions. The type I/typeII product ratio depends on the ring size; the six-membered ketone 6a is subject to typeIIreaction and the eight-membered ketone 6c is subject to type I reaction predominantly. The cyclization/elimination ratio of the typeIIreaction of 6 also depends on the ring size; the ratio decreases with