Recent advances and applications of Glaser coupling employing greener protocols
Symmetrical 1,3-diynes and their derivatives are useful motifs for the construction of complex molecules, and their excellent photochemical and material properties received considerable attention in the last decades. They are used for the synthesis of a large variety of polymers, biologically active molecules, supramolecular materials and light harvesting systems. Glaser coupling is the most widely used procedure for the synthesis of 1,3-diynes through the oxidative homocoupling of terminal alkynes. Classical homocoupling is catalysed by copper salts in the presence of a base and an oxidant. Numerous modifications were developed recently to improve the efficacy of Glaser coupling reactions. Novel synthetic routes and approaches employing greener protocols are well appreciable. In addition to terminal alkynes, other susceptible substrates are also tested for the synthesis of 1,3-diynes. These recent advances and perspectives of Glaser coupling reactions are documented in this review. This review highlights the diverse and innovative strategies developed for the synthesis and applications of 1,3-diynes expending green chemistry.