The α-tertiary amine motif drives remarkable selectivity for Pd-catalyzed carbonylation of β-methylene C–H bonds

The selective C–H carbonylation of methylene bonds in the presence of traditionally more reactive methyl C–H and C(sp(2))–H bonds in α-tertiary amines is reported. The exceptional selectivity is driven by the bulky α-tertiary amine motif, which we hypothesise orientates the activating C–H bond proximal to Pd in order to avoid an unfavourable steric clash with a second α-tertiary amine on the Pd centre, promoting preferential cyclopalladation at the methylene position. The reaction tolerates a range of structurally interesting and synthetically versatile functional groups, delivering the corresponding β-lactam products in good to excellent yields.