Optimization of the Light-Driven Contra-Thermodynamic Chain Walking Isomerization of Olefins

Abstract

The contra-thermodynamic isomerization of internal olefins to their terminal counterparts is an understudied but powerful synthetic tool that would have widespread applications in multiple industries given the ubiquity of olefins. Current methods rely on stoichiometric amounts of reagents to overcome the energy barrier associated with the decreased stability of the terminal product or are only capable of short-range transposition. This work reports on preliminary efforts towards the optimization of a novel isomerization strategy employing metal chain-walking using Schwartz’s reagent and a cobaloxime catalyst in a visible-light-driven reaction to convert trans-4-octene to 1-octene via the formation of an alkyl radical intermediate that is subsequently dehydrogenated to generate the product and refurnish the active catalyst to continue the cycle. An extensive cobaloxime catalyst screen was conducted to investigate which candidates furnished high yields and minimal amounts of the n-octane byproduct. Co(dmgH)\(_{2}\)(N-MeIm)Cl was identified as the best-performing candidate and attempts to synthesize an improved catalyst based on reactivity trends had limited success. The method was further developed by examining reaction conditions that improved yield and minimized the generation of byproducts. Future experimental directions including mechanistic studies to elucidate the potential pathways for the reaction which would in turn help inform modifications to be made to enhance the efficacy of the catalytic system are proposed.