Ligand-Enabled Cp ^E Rh ^III -Catalyzed C( <i>sp</i> ³ )–H Alkynylation of Carboxamides

A catalytic strategy that harnesses the carbonyl group of carboxamides to direct the site-selective alkynylation of C(sp3)–H sites was discovered. This protocol relies on the use of an electron-deficient CpERhIII complex and a 2-pyridone ligand to facilitate the formation of new C(sp3)–C(sp) bonds at both primary and secondary β-C(sp3)–H sites. This catalytic system also facilitated the C(sp3)–alkynylation of cyclopropane carboxamides to afford a series of alkynylated cyclopropane scaffolds that were amenable to further derivatization at both the amide and alkyne functionalities. The utility of this methodology was further exemplified through the functionalization of pharmaceutical derivatives and the rapid synthesis of drug conjugates.