Au(I)/Au(III) Catalytic Allylation Involving pi-Allyl Au(III) Complexes

A (MeDalphos)AuCI complex was found to efficiently catalyze the cross-coupling of indoles and ally! acetates/alcohols. The reaction tolerates many functional groups and selectively affords the branched C3-allylated products from both alpha- and gamma-substituted allyl substrates. It takes the advantage of the hemilabile character of the P<^>N ligand. The C(sp(2))-C(sp(3)) coupling operates via a Au(I)/Au(III) redox cycle and involves a dicationic pi-allyl Au(III) complex as a key intermediate. In this case, the allyl moiety adopts an asymmetric sigma + pi-coordination mode, as substantiated by NMR spectroscopy and density functional theory (DFT) calculations.