Direct Alkylation of Glycine Derivatives via Photoinduced Palladium Catalysis, Utilizing Intermolecular Hydrogen Atom Transfer Mediated by Alkyl Radicals

Abstract

Unveiling the alkyl/Pd hybrid species is a unique sp3-C-centered radical for facilitating intermolecular hydrogen atom transfer (HAT) in the development of direct alkylation of glycine derivatives. This transformative reaction proceeds smoothly under simple and mild conditions, exhibiting impressive versatility in terms of substrate scope encompassing both glycine derivatives and alkyl bromides while showcasing remarkable tolerance toward diverse functional groups. To shed light on the underlying mechanism, extensive investigations involving control experiments, deuterium labeling, radical clocking, and kinetic studies have been conducted. The collected data consistently support a reaction pathway involving the formation of Pd(I)/alkyl hybrid species followed by intermolecular HAT and elimination steps that lead to the in situ formation of imine intermediates, ultimately culminating in the final stage through radical addition.