Practical Synthesis of Chiral Ferrocenenylphosphino-Gold(I) Catalysts and NEST Analysis of the Enantioinduction

Abstract

The concise modular synthesis of a family of monodentate 1,2-disubstituted ferrocene ligands containing a diaryl phosphine and a 2-aryl indole is described. Their gold(I) complexes were applied to the enantioselective gold(I)-catalyzed formal [4 + 2] cycloaddition of 1,6-arylenynes, the enyne cyclization/nucleophile addition of N-tethered 1,6-enynes, and the methoxycyclization of 1,6-arylenynes with high levels of enantioselectivity in all cases. Crystallographic and computational studies highlighted the relevant role of noncovalent interactions within the ligand scaffold and between the ligand and substrate in the modes of enantioinduction in the cyclization of unsaturated substrates. Our recently developed open-source tool NEST was applied to analyze the chiral pockets of the catalysts, which in combination with RDKit allowed us to understand the enantioselectivity in these reactions, paving the way for a predictive-based approach toward the rational development of chiral ligands for enantioselective Au(I) catalysis.