Electrochemical chemo- and regioselective arylalkylation, dialkylation and hydro(deutero)alkylation of 1,3-enynes

The development of general and efficient strategies for the construction of allenes is important due to their wide applications. Although few protocols have been developed via the 1,4-difunctionalization of 1,3-enynes under thermal or photoredox conditions, the mild and robust methodology for dicarbofunctionalization and hydroalkylation remains unexplored. In the present study, we report an electrochemical multicomponent protocol for the chemo- and regioselective difunctionalization of 1,3-enynes. In particular, 1,4-arylalkylation and unsymmetrical dialkylation have been realized via electro- and nickel dual catalysis using graphite/nickel foam and zinc/nickel foam as electrodes, respectively. The use of a Zn/reticulated vitreous carbon electrode led to efficient 1,4-hydro(deutero)alkylation in the absence of a metal catalyst. A wide range of structurally diverse tri- and tetra-substituted allenes were easily prepared with good efficiency and excellent regioselectivity under mild reaction conditions. Notably, a series of natural product- and drug-derived substrates could undergo late-stage functionalization to generate the corresponding complex allenes. The synthesis of allenes through 1,4-difunctionalization of 1,3-enynes typically requires preformed organometallic species, high temperature or specific alkyl radical precursors. Now an electrochemical multicomponent protocol for the chemo- and regioselective 1,4-difunctionalization of 1,3-enynes is reported, which uses alkyl bromides with aryl bromides, alkyl bromides or H2O/D2O as reagents for 1,4-difunctionalization.