Small-Ring Compounds. XI. Some New Cyclobutane, Cyclobutene and Cyclobutanone Derivatives Derived from the Adduct of Phenylacetylene with 1,1-Difluoro-2,2-dichloroethylene

The adduct (I) of phenylacetylene and 1,1-difluoro-2,2-dichloroethylene (obtained in 76% yield in 2 hours at 130º) has been shown to be 1,1-difluoro-2,2-dichloro-3-phenylcyclobutene. Hydrogenation of I yielded1,1-difluoro-3-phenylcyclobutane (II), while hydrolysis with concentrated sulfuric acid at 100º gave crystalline 2,2-dichloro-3-phenylcyclobutenone (III). The structure of III was firmly established by base-induced cleavage to 4,4-dichloro-3-phenyl-2-butenoic acid (IV) and by reduction to 3-phenylcyclobutanone. I was found to rearrange to 1,1-difluoro-2,4-dichloro-3-phenylcyclobutene (VIII) on heating with triethylamine. VIII on hydrolysis with concentrated sulfuric acid yielded 2,4-dichloro-3-phenylcyclobutenone (IX), the structure of which was established by reactions similar to those used for III and reduction to phenylcyclobutane. IX displayed no tendency to yield 1-acetoxy-2,4-dichloro-3-phenylcyclobutadiene with isopropenyl acetate and p-toluenesulfonic acid under conditions where other ketones are converted to enol acetates.