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Amino acid esters serve as crucial intermediates in protein synthesis and as common structural elements in biologically active natural compounds. Herein, we present an efficient radical cascade reaction involving 1,2-nitrogen migration and C(sp2)–H intramolecular cyclization, enabling access to a diverse array of β-amino acid motifs. Upon cooperative Ni/diboron catalysis, a π-system-independent 1,2-N-shift of β-bromo α-amino acid esters is achieved, which allows the formation of two new bonds, including a C(sp3)–C(sp2) bond and a C(sp3)–N bond. The cascade reaction exhibits extensive substrate compatibility and high diastereoselectivity and proceeds without the need for oxidants, toxic radical initiators, and/or elevated temperatures. It has been observed that diboron compounds serve as both an activating reagent for inert C–N bond cleavage/migration and a reductant for the Ni catalytic cycle. This sheds light on the radical remote migration of N-functionalities without the need for π-systems. The radical cascades involving a 1,2-N-shift followed by intermolecular halogenation or selenation are also demonstrated.
Hong et al. (Thu,) studied this question.