LAUSR

We describe the (3 + 2) cycloaddition reaction of endocyclic N-silyl enamines and N,N'-cyclic azomethine imines. This process utilized the versatile endocyclic N-silyl enamine intermediates from the dearomative hydrosilylation of N-heteroarenes. The resulting tetracyclic pyrazolidinone structure was synthesized by a straightforward and atom-economical process. We also discussed the plausible origins of the different reactivity and endo/exo selectivity in terms of the structures of each proposed transition state. The successful gram-scale synthesis demonstrated the synthetic utility.