Route to 3-Amidino Indoles via Pd(II)-Catalyzed C–H Bond Activation

We report a facile synthesis of 3-amidino indoles from indoles and cyanamides. The reaction is Pd(II)-catalyzed and proceeds via C–H bond activation of the indole in its 3-position followed by a 1,2-addition of the resulting indole–palladium σ-complex to a cyanamide, which provides the corresponding amidine. The preference for 4,5-diazafluoren-9-one (DAF) as the ligand is investigated using DFT calculations, and a plausible reaction pathway is presented.