Oxidative reactions of azines 5.* ketodihydroxylation and coupling of 4-(γ-pyridyl)-1,2,5,6-tetrahydropyridines with acetone. Molecular and crystal structure of 3,4-dihydroxy-4-(γ-pyridyl)-1-ethylpiperidin-2-one

Oxidative coupling of 1-alkyl(benzyl)-4-(γ-pyridyl)-1,2,5,6-tetrahydropyridines with acetone in the presence of KMnO4 follows two pathways and yields both 1-R-2-(acetylmethylene)tetrahydropyridines and 1-R-3,4-dihydroxypiperidin-2-ones. When acetonitrile is used instead of acetone, the reaction under similar conditions occurs as selective ketodihydroxylation of the starting piperideines yielding 1-R-3,4-dihydroxy-4-(γ-pyridyl)piperidin-2-ones. The molecular and crystal structures of one of these products (R = Et) was studied by X-ray diffraction analysis.