A new and very efficient route to polycyclic heterocycles with isosteric replacement of benzene by pyridine is reported. This strategy involving the RCM reaction in pyridinic series as a keystep allows us to prepare 2H-dihydropyrano-or 2, 3H-dihydrooxepino [3, 2-b] pyridines 1 and 2 in very good overall yields (47% and 44%, respectively).