The versatile role of norbornene in C–H functionalization processes: concise synthesis of tetracyclic fused pyrroles via a threefold domino reaction

The synthesis of novel tetracyclic fused pyrroles from 1-(2-iodophenyl)-1H-pyrrole and various bromoalkyl-aryl alkynes via a palladium(0)-catalyzed and norbornene-mediated threefold domino reaction is reported. PdCl2 and tri-2-furylphosphine (TFP) in the presence of norbornene and Cs2CO3 in CH3CN at 90 °C gave a variety of tetracyclic fused pyrroles in usually high yields. In the described reaction sequence two of the three carbon–carbon bonds are formed by functionalization of an unactivated aryl C–H bond.