UC Santa Barbara
Homogeneous Gold Catalysis: Ligand Design and Reactions of Alkynes
- Author(s): Wang, Yanzhao
- Advisor(s): Zhang, Liming
- et al.
In the past dozen years, great progress has been made in developing highly efficient homogenous gold catalysis. As soft Lewis acids, cationic gold(I) complexes are particularly powerful in terms of activating alkyne/allene towards nucleophilic attack, leading to a variety of synthetically versatile structures. During my research, several synthetic methods have been developed, including: (1) Au-catalyzed ligand-directed anti nucleophilic attack of alkynes; the new ligands I developed enable highly efficient gold-catalyzed nucleophilic addition of acids, anilines and water to the alkynes; and catalyst loadings could be lowered to 10 parts per million; (2) rapid access of chroman-3-ones via gold-catalyzed oxidation of propargyl aryl ethers; this step-economic and efficient transformation was realized by a bulky gold catalyst, Me4tBuXPhosAuNTf2 and bulky electron-deficient pyridine N-oxides derived from Hantzsch esters; (3) Au-catalyzed novel indole synthesis via a key [3,3] sigmatropic rearrangement; 2-alkylindoles were produced with high regioselectivity and efficiency from easily accessed N-arylhydroxylamines under mild conditions; an improved approach involved cooperative dual catalysis of Zn and Au was developed; much broader substrate scope, shorter reaction time and good to excellent yields were achieved.