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. Although significant efforts have been recently made towards more sustainable conditions, including the use of recoverable catalysts and green solvents, 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. In this context, infrared (IR) light represents a very promising tool for fast, cheap and green organic synthesis. 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.
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