Tandem inverse electron demand Diels–Alder, retro-Diels–Alder and intramolecular Diels–Alder sequences: one-pot synthesis of diaza-polycycles

A new and straightforward methodology is described for the construction of complex nitrogen-containing polycycles from substituted 1,2,4-triazines and enamines, prepared in situ from carbonyl components and allylic amines. The transformation proceeds via a pericyclic reaction cascade (inverse electron demand Diels–Alder then retro-Diels–Alder then intramolecular Diels–Alder) forming the polycyclic systems in good to excellent yield and with high diastereoselectivity in a one-pot procedure. The scope and limitations of the methodology are described as are preliminary studies to extend its synthetic utility.