Electrochemical Ni–H catalysis for selective tail-to-tail reductive dimerization of terminal alkynes to access 2,3-dibranched butadienes

Abstract

Reductive dimerization of terminal alkynes offers a direct route to synthesize diverse 1,3-diene frameworks, including linear, 1,3-, and 2,3-branched structures. Achieving precise regioselectivity, particularly for 2,3-dibranched butadienes, remains a significant challenge. Here, we present an electrochemical nickel hydride (Ni–H) catalytic system for tail-to-tail reductive dimerization of terminal alkynes, enabling the selective synthesis of 2,3-dibranched butadienes. This method efficiently converts both aromatic and aliphatic terminal alkynes, including those with sensitive functional groups, and achieves cross-dimerization between aromatic and aliphatic alkynes. Cyclic and square wave voltammetry studies confirm a direct interaction between terminal alkynes and Ni(II)–H species, while kinetic analyses reveal that alkyne insertion is a key step and that the electrochemical reduction of Ni(II) to Ni–H governs the reaction efficiency. These findings advance the development of selective and efficient strategies for constructing complex 1,3-diene motifs.