Merging Gold Complexes With Chiral Phosphoric Acids For Asymmetric Catalysis And Au-Catalyzed Dearomative Coupling Reactions

In homogeneous catalysis,Au(I)complexes were well-known as strong π-Lewis acids.Their unique ability to activate carbon-carbon multiple bonds contributes to their widespread use in organic synthesis,leading to a variety of novel transformations.However,there is a disadvantage inherent to Au(I)complexes in terms of asymmetric catalysis.The linear geometry structure of Au(I)complexes makes chiral induction of ligands less efficient,resulting in the difficulty to achieve high enantioselectivity in asymmetric gold catalysis.The study of chiral gold complexes in homogeneous catalysis has a very short history and has mainly been carried out over the past 15 years.Most of investigations are focused on special chiral ligands,chiral counterions and developing chiral Au(III)complexes.In addition,asymmetric gold and organocatalyst combined catalysis has been a strategy to control enantioselectivity in gold catalysis by introducing chiral organic catalysts.The research themes of this thesis have been focused on merging gold complexes and chiral phosphoric acids for asymmetric synthesis.By this strategy,we accomplished an intramolecular hydroamination/asymmetric Michael addition cascade reaction,leading to a series of chiral tetrahydrocarbazoles.We also realized an enantioselective C(sp2)-H bond functionalization reaction of phenols and an enantioselective aza-ene-type reaction of enamides with diazo compounds by means of Au(I)/chiral phosphoric acid combined catalysis.The challenge of the latter two projects lies in the fact that we have to solve chemo-and stereo-selectivity problems at the same time.During our investigation of the reaction between indoles and diazo compounds catalyzed by gold complexes,we isolated an unprecedented dearomative coupling product.We found that the chemoselectivity of the reaction was controlled by ligands.wherein the phosphine ligands favors C-H insertion product while carbene ligands tends to give the dearomative coupling products.This is a new type of reaction between indoles and metal carbenes,showing the distinctive character of gold catalysis.