Part A: Palladium(II)-Catalyzed Enantioselective Saucy-Marbet Claisen Rearrangement of Propargyloxy indoles to Quaternary Oxindoles and Spirocyclic Lactones. Part B: The Regioselective Oxidative Coupling of Phenols .

Abstract

Part A. The first catalytic, enantioselective Saucy-Marbet Claisen rearrangement has been developed. Palladium(II) catalysts with BINAP or t-BuPHOX ligands were discovered as superior in catalyzing Claisen rearrangements of proparyloxy-substituted indoles to generate oxindoles bearing allenyl-substituted quaternary centers. Mechanistic evidence firmly established the intermediacy of a [3,3\u27]-sigmatropic rearrangement vs ionic or stepwise processes. This method proved to be tolerant of a broad range of functional groups. Tandem reactions of the silyl-allene products provide rapid access to a variety of spirocyclic oxindoles in one operation. Part B. The formation of biaryl C-C bonds by oxidative reactions is a well-recognized process in biological systems, being the second most common way nature constructs C-C bonds. However, very little progress has been made in the development of catalytic, regioselective methods for the oxidative coupling of phenols. High throughput experimentation (HTE) was used to screen a series of redox-active Salen and Salan metal complexes in the presence of O2. Copper, manganese, vanadium and ruthenium-catalyzed oxidative coupling conditions were developed that efficiently afford biaryls from a number of phenols with high yield and regioselectivity