(Phenoxyimine)Nickel- and (Phenoxythiazoline)Nickel-Catalyzed C(sp$^2$)–C(sp$^3$) Suzuki–Miyaura Cross-Coupling with Aryl Boronic Pinacol Esters

Abstract

Suzuki-Miyaura cross-coupling is one of the most important named chemical reactions used in industrial synthesis. Although palladium catalysts are most often used for these reactions, catalysts that instead use first-row metals are of interest in part because they may offer complementary reactivity to the shortcomings of palladium catalysts, in addition to being more sustainable, lower cost, and usually less toxic. This work highlights nickel catalysts bearing phenoxyimine (FI) and phenoxythiazoline (FTz) ligands for C(sp$^2$)–C(sp$^3$) cross-coupling reactions, specifically expanding the scope of the Chirik group’s previously reported nickel-catalyzed Suzuki-Miyaura cross-coupling method from boronic acids and boronic neopentyl glycol esters to boronic pinacol esters. These substrates are of particular interest given their ease of installment on highly functionalized scaffolds via Miyaura borylation. Reaction conditions are optimized for this specific type of reaction, the reactivity of FI and FTz ligands are compared, and the expanded nucleophile scope is briefly investigated. The results herein demonstrate the applications these nickel complexes have toward C(sp$^2$)–C(sp$^3$) Suzuki-Miyaura cross-coupling and establish a method that can be used to cross-couple boronic pinacol esters.