Lignosulfonate/Dicationic Ionic Liquid Composite as a Task-Specific Catalyst Support for Enabling Efficient Synthesis of Unsymmetrical 1,3-Diynes with A Low Substrate Ratio

In Glaser heterocoupling reactions, one of the alkyne precursors have to be used in five to ten times of excess. This not only wasted the organic substrate, but also decreased the catalytic efficiency of the metal catalysts. To solve this problem, we prepared a lignosulfonate/dicationic ionic liquid composite via ion exchange process. The thereby obtained materials can be used as catalyst supports for preparing heterogeneous Cu-based catalysts. The supports and the catalysts were characterized by many physicochemical methods including FT-IR, elemental analysis (EA), FSEM, FTEM, XPS, and TG. Interestingly, the catalyst can enrich the alkynol component in the reaction system, thus enabling Glaser heterocoupling reactions of alkynols and phenylacetylenes to proceed well with a low substrate ratio. The substrate scope of the Glaser heterocoupling reaction, enriching effect of the composite support for the alkynol component, and recyclability of the catalyst were also investigated.