Methylation of C(sp3)-H/C(sp2)-H Bonds with Methanol Catalyzed by Cobalt System

A highly efficient Co-based catalytic system, composed of a commercially available Co salt, a tetradentate phosphine ligand P(CH2CH2PPh2)(3)(PP3), and a base (denoted as [Co]/PP3/base), is developed for the methylation of C(sp(3))-H and C(sp(2))-H bonds using methanol as a methylating reagent. The Co(BF4)(2)center dot 6H(2)O/PP3/K2CO3 catalytic system showed high catalytic activity for the methylation of C-H bonds in aryl alkyl ketones, aryl acetonitriles, and indoles, with wide substrate scope and good functional group tolerance, and methyl-substituted products were obtained in good to excellent yields at 100 degrees C. This cheap, readily available, and highly efficient Co-based catalytic system may have promising applications in methylation reaction using methanol.