An efficient approach to homocoupling of terminal alkynes: Solvent-free synthesis of 1,3-diynes using catalyticCu(ii) and base

We report an environmentally friendly, efficient method for transforming terminal acetylenes into 1,3-diynes based on catalytic amounts of a Cu(II) salt and base under solvent-free conditions. The developed process conforms to the principles of ‘green’ chemistry and addresses the shortage of such methods for the synthesis of 1,3-diynes. The reaction is quite general and results in good yields. Interestingly, the system also allows the synthesis of unsymmetric 1,3-diynes by cross-coupling of two different terminal alkynes. Finally, the catalyst can also be recycled.