Photochemical reduction of gem-dihalocyclopropanes. III. Debromination of some compounds containing two 1,1-dibromocyclopropane moieties

2,2,2',2'-Tetrabromo-1-phenylbicyclopropyl and 1,1-dibromo-2-(2,2-dibromocy clopropyl)methyl-2-phenylcyclopropane have been synthesized, analyzed by X- ray crystallographic techniques, and exposed to acetone-sensitized irradiat ion. The former compound, which was obtained as a single diastereoisomer, g ave a product mixture consisting of an undisclosed number of the correspond ing tribromides resulting from reduction at either ring. The latter tetrabr omide was separated into its diastereoisomers, which were irradiated separa tely. One of the diastereoisomers gave a mixture of tribromides caused by r eduction at either ring, whereas the other isomer was reduced regioselectiv ely at the phenyl-substituted ring and gave a mixture of cis- and trans-1-b romo-2-(2,2-dibromocyclopropyl) methyl-2-phenylcyclopropane.