Gold(I)-Catalyzed Synthesis of Heterocycles via Allene Oxide from Propargylic Alcohols.

A new mechanistic pathway of propargylic alcohol activation by gold(I) catalysis has been proposed toward the efficient synthesis of N-protected pyrroles, 5,6-dihydropyridin-3(4)-ones from N-protected 5-aminopent-2-yn-1-ol, and 5-aminopent-2-yn-1-ol. Control experiments support that the reaction proceeded via the neighboring group participation of the oxygen atom of propargylic alcohol to form an allene oxide intermediate where the nucleophilic heteroatom attacks intramolecularly. Further, this methodology is successfully extrapolated toward the atom-economic synthesis of hydroxyalkyl indoles and benzofurans.

Stereoselective Synthesis of Oxacycles via Ruthenium-Catalyzed Atom-Economic Coupling of Propargyl Alcohols and Michael Acceptors.

Synthesis of β-hydroxyenones and its application toward development of tetrahydro-4-pyran-4-one in an atom-economic fashion is limited. This manuscript describes a ruthenium-catalyzed atom-economic coupling of pent-2-yne-1,5-diols and Michael acceptors as an efficient route for the synthesis of β-hydroxyenones with excellent yields and high regioselectivity. The β-hydroxyenones further undergo a 6- cyclization under acid-catalyzed conditions to deliver the tetrahydro-4-pyran-4-ones with high diastereoselectivity.