Cooperative Carbene Photocatalysis for B-Amino Ester Synthesis

B-Amino acids are useful building blocks of bioactive molecules, including peptidomimetics and pharmaceutical compounds. The current limited accessibility to B-2,2-type amino acids which bear an a-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 B-2,2-amino esters with high regioselectivity. The generation of nitrogen-centered radicals derived from simple imides via a se-quence of deprotonation and single-electron oxidation allows for the subsequent addition to gem-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.