Cooperative Carbene Photocatalysis for β‑Amino Ester Synthesis

• Published in: Journal of the American Chemical Society 2023-10, Vol.145 (45), p.24486-24492
• Main Authors: Tanaka, Nao, Zhu, Joshua L., Valencia, Oniya L., Schull, Cullen R., Scheidt, Karl A.
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.3c09875

β-Amino acids are useful building blocks of bioactive molecules, including peptidomimetics and pharmaceutical compounds. The current limited accessibility to β2,2-type amino acids which bear an α-quaternary center has limited their use in chemical synthesis and biological investigations. Disclosed herein is the development of a new N-heterocyclic carbene/photocatalyzed aminocarboxylation of olefins, affording β2,2-amino esters with high regioselectivity. The generation of nitrogen-centered radicals derived from simple imides via a sequence of deprotonation and single-electron oxidation allows for the subsequent addition to geminal-disubstituted olefins regioselectively. The intermediate tertiary radicals then cross-couple with a stabilized azolium-based radical generated in situ to efficiently construct the quaternary centers. Mechanistic studies, including Stern–Volmer fluorescence quenching experiments, support the proposed catalytic cycle.