The role of reversible oxidative addition in selective palladium(0)-catalyzed intramolecular cross-couplings of polyhalogenated substrates: synthesis of brominated indoles.

A Pd(0)-catalyzed C-N bond-forming reaction leading to the synthesis of brominated indoles is described. The use of the phosphine ligand PtBu(3) is necessary for reactivity. It is proposed that the bulky ligand serves to prevent inhibition of the catalyst by facilitating reversible oxidative addition into the product C-Br bond. Intramolecular coupling of a vinyl bromide in the presence of an aryl iodide can take place, demonstrating unprecedented levels of selectivity.