Abstract 5, 6-dihydropyridine 1 is synthesized either by flash vacuum thermolysis of 1- azabicyclo [2.2. 2] oct-2-ene 3 or by dehydrochlorination over solid bases of N-chloro-1, 2, 5, 6-tetrahydropyridine 4 and characterized at low temperature by its 1 H and 13 C nmr and ir spectra.