Reductive Alkylation Reactions Using Tetramethyldisiloxane and Potassium Tert-Butoxide Via Reductive-Radical Polar Crossover

Abstract

Hypervalent silicon compounds have shown increasing applications and synthetic versatility throughout recent years due to their unique reactivity. In this study, the combination of alkoxide base and silicon hydride species – potassium tert-butoxide (KOtBu) and 1,1,3,3-tetramethyldisiloxane (TMDSO) – facilitates two different reactions involving the formation of C(sp3)-C(sp3) bonds: the hydroalkylation of vinylarenes (chapter 2), and the cross-electrophile coupling of alkyl halides (chapter 3). This simple system of commonly available reagents is suspected to form a hypercoordinate silicon complex capable of acting as a single-electron donor as well as a hydrogen-atom donor. In each chapter, the process of discovery, optimization, scope, and mechanistic investigations are described. In chapter 2, mechanistic studies suggest the dual radical and polar characteristic of the benzyl nucleophile reactive intermediate, proving the system undergoes the process of reductive-radical polar crossover (RRPC) Ultimately, the TMDSO and KOtBu reagent pair is thought to be synthetically useful in performing reactions in transition-metal-, photoredox-, and electrochemistry-free conditions, with a potentially larger number of transformations that have yet to be discovered. The formation of C(sp3)-C(sp3) bonds is fundamental in organic synthesis and continues to be an ongoing field of research. Overall, novel routes towards the hydroalkylation of vinylarenes and cross-electrophile coupling of alkyl halides was successful using commercially cheap and synthetically available starting materials.