Organic molecules based on (hetero)aryl structural units have been extensively investigated in recent years, ranging from compounds of biological or pharmaceutical interest to highly π-conjugated materials for organic optoelectronics. The development of efficient methods for the generation of aryl-aryl bonds is a key step for the synthesis of these systems. In this context, direct C-H bond arylation of (hetero)arenes has opened new approaches for the generation of aryl-aryl bonds, replacing the more traditional transition metal-promoted cross-coupling reactions with organometallic derivatives.[1] Although significant efforts have been recently made towards more sustainable conditions, including the use of recoverable catalysts and green solvents,[2] some issues still remain, such as the need of high temperatures and long reaction times.
The use of non-conventional heating sources has earned increasing attention, due to the possibility of minimizing reaction time, improving product yield and avoiding undesired byproducts.[3] In this context, infrared (IR) light represents a very promising tool for fast, cheap and green organic synthesis.[4] However, the true potential of IR-assisted reactions is still almost unexplored, especially for Palladium-catalyzed coupling chemistry.
Here we report the first IR light-assisted Palladium-catalyzed direct C-H bond arylation protocol, performed in solvent-free and non-anhydrous conditions. The reaction was successfully applied to several heteroarenes (benzothiophene, thieno[3,4-c]pyrrole-4,6-dione, 1,2,3-triazole, and pentafluorobenzene) with functionalized aryl iodides, giving the corresponding direct C-H bond arylation products in good yields after very short times.

[1]: D. Alberico, M. E. Scott, M. Lautens, Chemical Reviews, 2007, 107, 174-238, DOI: 10.1021/cr0509760.
[2]: S. Mao, H. Li, X. Shi, J.-F. Soulé, H. Doucet, ChemCatChem, 2019, 11, 269-286, DOI: 10.1002/cctc.201801448.
[3]: R. B. N. Baig, R. S. Varma, Chemical Society Reviews, 2012, 41, 1559-1584, DOI: 10.1039/C1CS15204A.
[4]: R. Escobedo, R. Miranda, J. Martínez, International Journal of Molecular Sciences, 2016, 17, 453, DOI: 10.3390/ijms17040453.