Green Light Promoted Iridium(III)/Copper(I)-Catalyzed Addition of Alkynes to Aziridinoquinoxalines Through the Intermediacy of Azomethine Ylides

This manuscript describes the development of alkyne addition to the aziridine moiety of aziridinoquinoxalines using dual Ir(III)/Cu(I) catalytic system under green LED photolysis (lmax = 525 nm). This mild method features high levels of chemo- and regioselectivity and was used to generate 29 highly functionalized substituted dihydroquinoxalines in 44-98% yield. This transformation was also carried asymmetrically using (S,R)-N-PINAP as the chiral ligand to provide 9 chiral addition products in 96:4 to 86:14 e.r. The experimental and quantum chemical explorations of this reaction suggest a mechanism that involves Ir(III)-catalyzed triplet energy transfer mechanism followed by a ring-opening reaction ultimately leading to the formation of azomethine ylide intermediates. These azomethine intermediates undergo sequential protonation/copper(I) acetelide addition to provide the products.