Sc(OTf)3-catalyzed dehydrogenative cyclization for synthesis of N-methylacridones.

A novel method has been developed for the synthesis of substituted N-methylacridones from 2-(N-methyl-N-phenylamino)benzaldehydes via dehydrogenative cyclization. This transformation involves two primary processes: the aldehyde first coordinates with Sc(OTf)3 and induces the aromatic electrophilic substitution (S(E)Ar) reaction to form the active intermediate N-methyl-acridin-9-ol, which is then quickly oxidized in situ to afford the acridones. Furthermore, the procedure involved is both environmental friendly and atom efficient; H2O is the only byproduct in this reaction.