Reactions of bicyclic olefins with palladium chloride–copper chloride

Abstract

endo-(1) and exo-5,6-(o-phenylene)norborn-2-ene (2) and endo-(3) and exo-5,6-(1,8-naphthylene)norborn-2-ene (4) have been prepared and their reactions with a palladium chloride–cupric chloride catalyst system investigated. Products with rearranged and unrearranged structure have been identified. The mechanism of these reactions has been discussed and it has been suggested that the controlling intermediate leading to unrearranged products is an olefincopper complex, whereas the corresponding palladium(II) complexes lead predominantly to rearranged chloroacetates. Species possessing carbonium ion character have been suggested as intermediates in the pathway involving palladium. Carbonium ion formation in the cupric chloride catalysed reactions is much less pronounced. The important role of substituents in determining the rearrangements has been demonstrated and confirmed by the reactions, in acid media, of the derived epoxides of olefins (1) and (2). Solvolytic studies involving a number of derived bromohydrins further emphasised the importance of this factor.