Cu(I)-Catalyzed Enantioselective [5 + 1] Cycloaddition of N‑Aromatic Compounds and Alkynes via Chelating-Assisted 1,2-Dearomative Addition

Copper-catalyzed
[5 + 1] cycloadditions of N-aromatic zwitterions
have been accomplished by chelation-assisted 1,2-dearomative addition
of electron-deficient terminal alkynes. The unique modular skeleton
of pyrazino­[1,2-a]­quinoline could be obtained from
the regio- and stereoselective cascade annulation process, which was
supported by computational studies. Further, an asymmetric variant
of the developed strategy has been successfully extended for enabling
access to optically enriched six-member cyclic systems.