[Brinda]

I tried to carry out a Cu catalyzed Ullmann coupling reaction of imidazole/benzimidazole with 2-iodo-1,3-dimethoxy benzene but it was not successful. I have tried doing this multiple times in the past four months by following different protocols, including the use of palladium as catalyst in the place of copper iodide/copper acetate, changing the solvent system from DMF to DMSO, toluene etc. I have used Cs2CO3 and K2CO3 in most of these reaction as they are known to be excellent base, also, have used an additional ligand like 1,10-phenanthroline. But I am unsuccessful in achieving the product. I would appreciate if someone could give some suggestion on what possibly I could do next to get the product.

P.S.I have also tried doing a neat reaction (absence of solvent and Cu) only with the base which again was not successful.
thank you in advance

[kriggy]

Your halide is quite electron rich which makes it not very reactive in thise case AND its sterically hindered. Also, those heterocycles are not exactly simple to arylate.
You can try metalic copper as a catalyst and heat that s#*$ up, you probably need 140°C or more.

OR you can try to convert the iodide into boronic acid (either Pd catalyzed borylation or just lithium-halogen exchange and then quench with borate) and then try another coupling. I think this paper even has the compoound you want to make (table 3, cpd 6j, table 4, cpd 8j)

Janíková, K., Jedinák, L., Volná, T., & Cankař, P. (2018). Chan-Lam cross-coupling reaction based on the Cu2S/TMEDA system. Tetrahedron, 74(5), 606–617. https://doi.org/10.1016/j.tet.2017.12.042