Photochemistry of $\alpha$, $\alpha$-Dihalovalerophenones

${\alpha}$,${\alpha}$-Dibromovalerophenone and ${\alpha}$,${\alpha}$-dichlorovalerophenone were prepared and their photochemical behaviors were investigated. The former gives C-Br cleavage products and the latter gives mainly the Yang photocyclization products upon irradiation. The reactivity of the chlorine substituted ketone turned out to be quite different from that of ${\alpha}$,${\alpha}$-difluorovalerophenone which gives both the cyclization and elimination products from the 1,4-biradical intermediate.