Base-promoted [3+2] annulation of

A base-promoted [3+2] cycloaddition between N-aminoisoquinolinium/N-aminoquinolinium derivatives and cyclic iodonium ylides/2,2-difluorovinyl tosylate has been developed, enabling efficient access to polycyclic pyrazolo[5,1-a]isoquinolines and 1-fluoropyrazolo[5,1-a]isoquinoline frameworks with good yields and broad substrate scope. Furthermore, the synthetic utility of this method was demonstrated by scale-up reactions and subsequent transformations of the resulting polycyclic products, highlighting its potential for the construction of structurally complex polycyclic N-heterocycles.