Functionalization of the benzobicyclo[3.2.1] octadiene skeleton possessing one isolated double bond via photocatalytic oxygenation

Abstract

Photocatalytic oxygenation of three phenyl derivatives of a bicyclic skeleton with a free double bond 1a, 1b and 1c were carried out by utilizing a cationic and an anionic manganese(III) porphyrin irradiated in the visible range. While photocatalysis of 1a and 1b led to the formation of the corresponding hydroperoxy derivatives 2 and 3, respectively, (besides unidentified high-molecular-weight products) in the presence of the anionic Mn(III) porphyrin, the cationic photocatalyst proved to be less efficient and less selective with 1a. In the case of 1b, also with the cationic porphyrin, the corresponding hydroperoxy derivative (3) was the main product at a shorter reaction time (2 h), whereas a longer irradiation (4 h) led to the significant formation of a keto derivative (5) with a hydroperoxy substituent and a free double bond at positions deviating from those in the previous products (2 and 3). A dramatic change in the reactivity was observed for the methoxy derivative (1c). It gave only traces of identifiable products by using the anionic photocatalyst, while application of the cationic Mn(III) porphyrin resulted in a relatively efficient formation of an epoxy derivative (6) due to the reaction of the isolated double bond.