In this work, the addition of 2-methylazaarenes benzylic sp(3) C-H to electron-deficient olefins, catalyzed by pepsin from pig gastric mucosa was reported. A series of azaarene derivatives (1 mmol) were obtained in good yields at 60 degrees C for 60 similar to 72 h with 20 mg pepsin as catalyst. This is a facile method and the reaction conditions are mild, which expands the application of biocatalysis in sp(3) C-H functionalization of azaarenes.