Tert-butylated ferrocenyl diphosphanes for palladium-catalyzed C5-arylation of 1,3,4-oxadiazoles with aryl triflates

A series of tert -butyl-substituted ferrocenyl diphosphanes were synthesized and evaluated as ligands in palladium-catalyzed direct C–H arylation reactions. Their coordination to palladium afforded well-defined complexes that were characterized by NMR spectroscopy and, in selected cases, by X-ray diffraction analysis. The electronic properties of the ligands were assessed through ¹ J (P,Se) coupling constants of the corresponding selenides. These palladium systems were applied to the direct C5 -arylation of 1,3,4-oxadiazoles using aryl triflates as electrophiles. Under optimized conditions, the transformation proceeds in the absence of additional additives and at relatively low catalyst loadings. A range of aryl triflates and substituted oxadiazoles was examined, showing moderate to good efficiency depending on the electronic and steric properties of the substrates. Comparative studies indicate that ligand structure influences catalytic performance, particularly with respect to steric demand and susceptibility to oxidation. Overall, these results provide insight into the behavior of ferrocenyl diphosphane ligands in palladium-catalyzed C–H activation processes involving challenging C–O electrophiles.