Synthesis of Carbene‐Metal‐Amido (CMA) Complexes and Their Use as Precatalysts for the Activator‐Free, Gold‐Catalyzed Addition of Carboxylic Acids to Alkynes

A straightforward synthetic protocol leading to carbene–metal–amido (CMA) complexes (metal=Au, Cu) using a mild base and an environmentally desirable solvent (EtOH) has been explored, with a focus on complexes bearing backbone‐substituted N‐heterocyclic carbene (NHC) ligands, including BIAN‐NHCs (BIAN=bis(imino)acenaphthene). The novel CMAs were structurally characterized, and gold‐based CMAs bearing diverse NHCs were screened as simple, Brønsted‐basic precatalysts. The readily accessible complexes display high catalytic activity in the intermolecular and intramolecular hydrocarboxylation of internal alkynes and alkynoic acids respectively, while the screening reveals the ancillary ligand effect of NHCs in these catalytic systems. A sustainable synthetic N−H metalation route to carbene‐metal‐amido (CMA) complexes bearing backbone‐modified (and classical) NHC ligands, carbazole and amines is presented. The CMAs are employed for the first time as precatalysts in the inter‐ and intramolecular addition of carboxylic acids to alkynes.