Copper-promoted site-selective carbonylation of sp3 and sp2 C–H bonds with nitromethane

Copper-promoted direct carbonylation of unactivated sp3 C–H and aromatic sp2 C–H bonds of amides was developed using nitromethane as a novel carbonyl source. The sp3 C–H functionalization showed high site-selectivity by favoring the C–H bonds of α-methyl groups. The sp2 C–H carbonylation featured high regioselectivity and good functional group compatibility. Kinetic isotope effect studies indicated that the sp3 C–H bond breaking step is reversible, whereas the sp2 C–H bond cleavage is an irreversible but not the rate-determining step. Control experiments showed that a nitromethyl intermediate should be involved in the present reaction.