RhIII-Catalyzed Redox-Neutral C-H Activation of Pyrazolones: An Economical Approach for the Synthesis of N-Substituted Indoles

A new strategy is reported for the economical synthesis of indoles bearing an N-(3-aminobut-2-enoyl) substituent through RhIII-catalyzed redox-neutral C-H activation of pyrazolones and alkynes. This approach utilizes cheap substrates and mild reaction conditions to access a unique class of indoles via a N-N bond oxidative cleavage without loss of the N-terminus, therefore meeting all the atom/step/redox economy principles.