Modular Construction of Unnatural α‐Tertiary Amino Acid Derivatives by Multicomponent Radical Cross‐Couplings

Although the synthesis of α‐tertiary amino acids (ATAAs) has been extensively studied, the development of an inexpensive and facile methodology to incorporate multifunctionality on ATAAs remains challenging. In this article, we present a single‐step radical approach for the modular synthesis of functionally diverse ATAAs. This synthesis takes place under mild conditions with an absence of metals, photocatalysts, and all other additives. We demonstrate the broad applications of this approach on a variety of aliphatic and aromatic carboxylic acids, alkenes, 1,3‐enynes, and oxazolones. The results prove that our method provides excellent functional group tolerance and late‐stage applicability, as well as gram‐scale synthesis via flow chemistry. Additionally, we include mechanistic studies which reveal that the excited state of oxazolone enolate upon light excitation is a key intermediate that acts as a radical precursor and an efficient reductant. Reported herein is a highly selective radical cascade‐cross‐coupling reaction for the modular synthesis of α‐tertiary amino acids (ATAA) under mild conditions. Mechanistic studies reveal the excited state of an in situ‐generated oxazolone enolate as a key intermediate, which functions both as a radical precursor and an efficient reductant.