Regioselective Photochemical C–OMe Bond Formation Initiated by One‐Electron Transfer and N–OMe Bond Fragmentation in Electron Donor–Acceptor Systems

Abstract

AbstractCompounds that integrate electron donor–acceptor subunits with N‐methoxyisoquinolinium as acceptors and substituted (methoxy)benzenes as donors were synthesized and their luminescent and photochemical properties studied. Photolysis yielded the corresponding photomethoxylation products in a two‐step process that involves N–OMe bond scission followed by C–OMe bond formation. Homolysis of the N–OMe bond restores the aromatic isoquinoline nucleus and produces a methoxy radical that can couple to the required ring carbon atom in the benzene cation radical to give the products in a regioselective process controlled by the spin density of the cation radical. This photoprocess involves two different pathways: methoxylation of the acceptor (intracomponent methoxylation) or the donor (intercomponent metoxylation). Both methoxy‐transfer pathways are controlled by the donoating ability (redox potential) of the donor subunit, consistent with the emission observed upon excitation of the charge‐transfer state in systems that undergo intermethoxylation.