π‐Extended DPCB for Activation‐Free Homogeneous Gold Catalysis

Abstract

Abstract The catalytic properties of bis[chlorogold(I)] complexes that bear the 3,4‐bis(2,4,6‐tri‐ tert ‐butylphenyl)‐3,4‐diphosphinidenecyclobutene (DPCB) ligand could be improved by suitable extension of the π‐conjugation. If the 1‐naphthyl substituent was employed in the 1,2‐positions in the kinetically stabilized DPCB skeleton, high catalytic activity of the DPCB‐bis(chlorogold) complex was induced in the intermolecular alkoxycyclization of 1,6‐enyne without activation by a Ag cocatalyst. DFT calculations of the 1,2‐diaryl‐substituted DPCB derivatives indicated that both suitable energetic reduction of the LUMO level and steric characteristics of the ligand structure are important for the high catalytic activity. The optimized 1‐naphthyl‐substituted DPCB‐chlorogold(I) complex was further employed for catalytic intramolecular cyclizations to afford heterocyclic structures by the activation of terminal acetylene and allene moieties and the hydration of terminal acetylene under the mild conditions.