Catalyst-controlled directing group translocation in the site selective C–H functionalization of 3-carboxamide indoles and metallocarbenes

Complementary methods toward the selective functionalization of indole and oxindole frameworks employing an alternative strategy in heteroaryl C–H functionalizations are presented herein. This work focuses on a catalyst-controlled, site selective C–H activation/functionalization of 3-acyl indoles, wherein an amide serves as a robust and versatile directing group capable of undergoing concomitant 1,2-acyl translocation/C–H functionalization in the presence of a RhI/AgI co-catalysts to provide the cross-coupled adducts in high yields. In contrast, the use of IrIII/AgI catalysts subverted the 1,2-acyl migration to afford the corresponding C2-functionalized products in good to excellent yields. A notable feature of the catalyst systems was the exceptional level of site selectivity observed in which the corresponding C–H functionalized indoles were obtained exclusively. Mechanistic experiments indicate a concerted 1,2-acyl migration step and indole metallation occurring through an electrophilic aromatic substitution process.