The hetero-Diels-Alder reaction catalyzed by lanthanum triflate hydrate using diethyl azodicarboxylate as dienophile, yielding differently substituted 1,2,3,6-tetrahydropyridazines, is described.
GOLLNICK, K.;GRIESBECK, A., TETRAHEDRON LETT., 1983, 24, N 32, 3303-3306