Fig. 1: Importance of 3D N-rich bridged compounds, previous work and reaction design.

a, The importance of 3D heterocycles. b, Examples of natural products possessing N-rich bridged heterocyclic ring systems. c, Classes of azomethine imines, and traditional synthetic approaches towards their preparation. d, This work, targeting the synthesis of C,N,N-cyclic azomethine imines 7 and their cycloadditions with various dipolarophiles 8. IP, intellectual property; SAR, structure–activity relationships; NPR, normalized principal moment of inertia ratios.