Recent Developments in the Direct Methylation of Electron-Deficient N-Heteroarenes

The direct introduction of methyl groups into electron-deficient N-heteroarenes has recently emerged as an efficient and promising strategy to afford methylated N-heteroarenes, which are important motifs in a variety of pharmaceuticals and biologically active molecules. Herein, three general state-of-the-art approaches including radical-mediated, transition-metal-catalyzed, or transition-metal-free direct C-H methylations of electron-deficient N-heteroarenes are highlighted.