The Cu (1) salt catalyzed reaction of benzoyl peroxide with benznorbornadiene leads to the expected substitution product anti-7-ben~ oyloxybenznorbornadiene1 although in lower yield than a previous reported. In addition, the reaction yields up to 10% of a heretofore unknown hydrocarbon which has been identified as a phenylation product of benznorbornadiene. The structure of the phenylation product is shown to be anti-7- ...