Pyridine-enabled copper-promoted cross dehydrogenative coupling of C(sp2)-H and unactivated C(sp3)-H bonds

The pyridine-enabled cross dehydrogenative coupling of sp(2) C-H bonds of polyfluoroarenes and unactivated sp(3) C-H bonds of amides was achieved via a copper-promoted process with good functional group compatibility. This reaction showed great site-selectivity by favoring the sp(2) C-H bonds ortho to two fluoro atoms of arenes and the sp(3) C-H bonds of a-methyl groups over those of the amethylene, b-or g-methyl groups of the aliphatic amides. Mechanistic studies revealed that sp(3) C-H bond cleavage is an irreversible but not the rate-determining step, and the sp(2) C-H functionalization of arenes appears precedent to the sp(3) C-H functionalization of amides in this process.