Iridium catalysis for C-H bond arylation of heteroarenes with iodoarenes.

Efficient couplings using equimolar quantities of each coupling partner and multiple C-H bond arylation reactions are achieved with an Ir-based catalytic system for the C-H bond arylation of electron-rich heteroarenes with iodoarenes to construct extended pi-systems. The dramatic ligand effect on reaction efficiency leads to the discovery that Crabtree's catalyst (see scheme) is the optimal catalyst precursor.