Ruthenium-catalyzed redox-neutral C-H activation via N-N cleavage: synthesis of N-substituted indoles.

The first Ru-catalyzed redox-neutral C-H activation reaction via N-N bond cleavage is reported. Pyrazolidin-3-one is demonstrated as an internally oxidative directing group that enables C-H annulation reactions with a broad scope of alkynes, including previously incompetent terminal alkynes. Pharmacologically privileged 3-(1H-indol-1-yl)propanamides were synthesized in high yields.