Photocycloelimination of alpha,alpha-dichlorocyclobutanones

Direct irradiation of a series of alpha,alpha-dichlorocyclobutanones in ben zene solutions results in photocycloelimination to give 1,1-dichloroalkenes in yields ranging from 30-65%. The alpha,alpha-dichlorocyclobutanones were formed in good yields from the [2+2] cycloaddition of the terminal olefins with dichloroketene. This two-step sequence formally represents a "metathe sis" of two olefinic functions and provides an easy access to functionalize d 1,1-dichloroalkenes. Irradiation of the dichlorocyclobutanones in the sol id state led to poor yields of 1,1-dichloroalkenes and polymeric mixtures, however, photoreactions performed in zeolites gave similar yields as those run in benzene solutions.