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

Abstract

The pyridine-enabled cross dehydrogenative coupling of sp2 C–H bonds of polyfluoroarenes and unactivated sp3 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 sp2 C–H bonds ortho to two fluoro atoms of arenes and the sp3 C–H bonds of α-methyl groups over those of the α-methylene, β- or γ-methyl groups of the aliphatic amides. Mechanistic studies revealed that sp3 C–H bond cleavage is an irreversible but not the rate-determining step, and the sp2 C–H functionalization of arenes appears precedent to the sp3 C–H functionalization of amides in this process.