Photoinduced Copper(II) Catalyzed Decarboxylative Homocoupling of Arylpropiolic Acids: A Facile Access to the Symmetrical 1,3‐Diynes

Abstract

We have developed an efficient visible light induced copper‐mediated protocol to synthesize conjugated 1,3‐diynes via decarboxylative homocoupling of arylpropiolic acids. A variety of electron‐rich and electron‐deficient acids worked well in this methodology providing desired product upto 99% yield. Detailed mechanistic investigations including UV‐Vis spectroscopy and in‐situ IR experiments have been carried out to elucidate the plausible reaction mechanism. Compared to previously reported thermal strategies, this new pathway occurs at room temperature, employs greener solvent and aerial oxygen as an oxidant.

Advancements in double decarboxylative coupling reactions of carboxylic acids

“…With the objective of designing a milder procedure to 1,3-diynes through the oxidative decarboxylative homocoupling of propiolic acids, very recently Pathania and Roy were able to demonstrate that a library of symmetrical 1,4-di(hetero)arylsubstituted 1,3-diynes 48 could be obtained in high to excellent yields (up to 98%) from the respective (hetero)aryl propiolic acids 47 using CuCl 2 /phen/K 2 CO 3 combination as a catalytic system under the irradiation of visible light at room temperature ( Scheme 24 ). 26 Notably, the presence of catalyst, ligand or light was crucial for the success of this transformation. The reaction was completely shut down in the absence of any of them.…”