Oxidative reactions of azines. 6. Lactamization of 4-aryl- and 4-phenethenyl-substituted 1,2,3,6-tetrahydropyridines and dihydroxylation of 4-aryl-1,2,5,6-tetrahydropyrid-2-ones using potassium permanganate

Oxidation of 4-phenyl-, 4-(4-pyridyl)-, and 4-phenethenyl-1,2,3,6-tetrahydropyridines with potassium permanganate can stop at the stage of the introduction of an oxo group into the allyl C(2) position of the piperideine fragment. In contrast to their precursors, 4-aryltetrahydropyridin-2-ones obtained in this way can be converted to 3,4-dihydroxy-2-oxopiperidines under Wagner reaction conditions.