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.