Silver-Free Gold-Catalyzed Heterocyclizations through Intermolecular H-Bonding Activation

J Org Chem. 2023 Feb 17;88(4):2487-2492. doi: 10.1021/acs.joc.2c02932. Epub 2023 Jan 26.

Abstract

Modulable monosulfonyl squaramides have been shown to exert activation of gold(I) chloride complexes through H-bonding in an intermolecular way. Combinations of (PPh3)AuCl or IPrAuCl complexes and an optimal sulfonyl squaramide cocatalyst bearing two 3,5-bis(trifluoromethyl)phenyl groups efficiently catalyzed diverse heterocyclizations and a cyclopropanation reaction, avoiding in all cases undesired side reactions. Computational studies indicate that the Au-Cl bond breaks by transligation to the triple bond in a ternary complex formed by the actual AuCl···HBD catalyst and the substrate.