Multicomponent [5 + 2] Cycloaddition Reaction for the Synthesis of 1,4-Diazepines: Isolation and Reactivity of Azomethine Ylides

Air-stable
azomethine ylides with an unusual pattern of charge
distribution were efficiently prepared via the rhodium-catalyzed reaction
between pyridines and 1-sulfonyl-1,2,3-triazoles. This reaction allowed
for the first example of the catalytic multicomponent [5 + 2] cycloaddition
reactions, thus resulting in the formation of biologically active
1,4-diazepine compounds.