One-pot transition-metal-free synthesis of alkynes and enynes

Alkynes are key motifs in chemistry, serving as precursors in many organic reactions toward the synthesis of bioactive compounds, polymers, and new materials. Methods to synthesize terminal alkynes with an extension of the carbon skeleton involve harsh and/or dangerous reagents. Further derivatization of terminal alkynes to diaryl alkynes largely relies on the popular Sonogashira coupling. This cross-coupling uses expensive Pd catalysts, phosphine ligands, and toxic Cu co-catalysts. Herein, we report a one-pot approach to diaryl alkynes under transition-metal-free conditions from feedstock chemicals (toluenes and methyl benzoates). This approach is also applicable to the preparation of conjugated 1,3-enynes in a single flask. The disclosed methods are expected to be complementary to the state-of-the-art by streamlining the synthesis of alkynes, reducing the costs of production of these valuable building blocks, and increasing the sustainability of the synthesis of alkynes.