Synthesis and Transformations of Novel Acetylene Glycols Derived from N-Substituted Piperidin-4-ones.

With the aim to prepare asymmetric acetylenic γ-glycols, the reactions of 1-(2-ethoxyethyl)piperidin-4-one with propargyl alcohol were studied and the reaction conditions were optimized to reach satisfactory yields of the target glycols. Some transformations of the γ-glycols were studied. It was found that the reaction of 1-(2-ethoxyethyl)-4-(3-hydroxyprop-1-yn-1-yl)piperidin-4-ol with ethyl bromide involves exclusively the OH group on the quaternary carbon atom to form a monoethyl ether, and the mercury-catalyzed hydration involves cyclization with the elimination of a water molecule from the keto glycol moiety, leading to a spiroketone. It was shown that the catalytic reduction of 1-(2-ethoxyethyl)-4-[2-(1-hydroxycyclohexyl)ethynyl]piperidin-4-ol at atmospheric pressure produces a mixture of a saturated and an unsaturated products in a 1 : 2 ratio. Quantum-chemical calculations of the stable conformers of the synthesized asymmetric acetylenic γ-glycols were performed by the RHF/STO-3G method with geometry optimization using Gaussian 09 software. [ABSTRACT FROM AUTHOR]