Development of Nickel-Catalyzed Methods for Deoxygenation Processes

Abstract

A new method for the reductive coupling of enals or enones and alkynes has been developed. The method results in a unique net four-electron reduction of the starting materials, leading to the formation of a deoxygenated 1,4-diene product. During the optimization of the reaction, a discrete nickel catalyst was synthesized, resulting in much higher levels of reactivity. The proposed reaction mechanism highlights the dual functionality of the titanium additive, as both a reductant and Lewis acid. This unique characteristic was then applied to the development of other novel organic reactions. The method also offers an improved substrate scope over analogous methods to synthesize 1,4-dienes. Silyl protecting groups represent a powerful synthetic tool in organic chemistry. Despite their widespread use in synthesis, little work has been done in the activation of the C-O bond of silyl ethers. Utilizing mechanistic information obtained from previous work, the functionalization of silyl aryl ethers were explored using nickel catalysis. Through extensive optimization, the nickel-catalyzed reduction, silylation, and amination of silyl aryl ethers is reported. The methodology offers improved reaction conditions and substrate scopes compared to analogous carbon-oxygen bond functionalization reactions.