Light-Induced Self-Nitrosation of Polycyclic Phenols with Nitrosamine. Excited State Proton Transfer

Article abstract of DOI:10.1021/ja00251a034

Photoexcitation of polycyclic phenols in the presence of N-nitrosodimethylamine caused the self-nitrosation of the phenols to give 1,2- or 1,4-quinone monooximes.With use of naphthols as models, the key step of the photonitrosation was shown to be a dual sensitization process from the lowest singlet excited state of naphthols by proton transfer followed by energy migration within an exciplex to cause the known homolysis of the nitrosamine; it is assumed that the resulting radical species undergo nitrosation of naphtholates.The crucial requirement of the excited state proton transfer (ESPT) reaction is established by quenching of the photonitrosation by general bases, such as water and TEA, with quenching rate constants close to those of naphthol fluorescence by these bases.