Organic photochemistry with 6.7eV photons: 1,2,5,6-tetrahydropyridines and tropidine

Irradiation of the title compounds in hydrocarbon solutions with 185nm light leads to retro-Diels-Alder reactions as the principal process. The imine fragment, CH2=C-CH3 undergoes efficient trimerization, a process which may be promoted by molecular association of the reactant. © 1979.