A very straightforward route to 1-azabicyclo alkaloid scaffolds with several ring sizes is reported. The final bicyclic structures were built through a synthetic scheme that involved (i) the construction of dienic 4-piperidone systems by an imino-Diels−Alder reaction between aminotrienes and N-ω-vinylimines, in the presence of Yb(OTf)3, and (ii) the ring-closing metathesis reaction of these cyclic