Pentynenones Formation Through Copper Catalyzed Coupling-isomerization Reaction Between Alkynyl Bromides And Propargylic Alcohols

Pentynenones is a class of compounds containing conjugated C≡C, C=C, and C=O bonds, which are widely present in natural products and possess potential biological activity. Meanwhile, pentyneones are a very important class of organic synthesis intermediates due to the basic properties of isolated alkynyl, vinyl and carbonyl group as well as unique properties derived from the conjugation betweeen the triple bond, the double bond and carbonyl groups, and are widely applied in the synthesis of a number of heterocyclic compounds, such as furan, pyrazole, oxide derivatives, dihydro-thiopyran, and total synthesis of natural products or drugs.After studying the literatures, we found that the commonly used synthetic methods is to use alkyne and their derivatives as the precursor to synthesize pentynenones.In organic synthesis chemistry, haloalkynes is an important class of synthetic intermediates, and are used as both electrophilic and nucleophilicity reagent. In transition metal-catalyzed systems, capable of showing rich reactivity. Since the halogen atom directly conneted with C≡C bond with sp hybrid in haloalkynes structure, such haloalkynes have both controllable electrophilic and nucleophilicity.In this article, we found that 1,5-Disubstituted(E)-pent-2-en-4-yn-1-ones can be exclusively synthesized by copper-catalyzed tandem coupling-isomerization reaction of alkynyl bromides and secondary propargylic alcohols in piperidine. The mechanistic investigations suggest that piperidine plays a duel role being both a solvent and a base in the reaction.