Pseudopericyclic dearomative 1,6-cyclization of 1-(2-pyridyl)-2-azabuta-1,3 dienes: synthesis and ring-chain valence equilibria of 4H-pyrido[1,2-a]pyrazines

In this work, we studied 1,6-electrocyclizations of 1-(2-pyridyl)-2-azabuta-1,3-dienes 3 as representatives of 1,4-diazahexatrienes with the C=N bond incorporated in aromatic pyridine system. 2-Azadienes 3 for the study were synthesized by the Rh(II)-catalyzed reaction of triazolopyridines 1 with 2H-azirines 2.This work was done under support of the RSF (grant 19-73-10090) using resources of the Magnetic Resonance Research Centre, Chemical Analysis and Materials Research Centre, Centre for X-ray Diffraction Studies, Computing Centre of the Research Park of St. Petersburg State University