A distinct C-H activation-based traceless synthetic protocol via electrophilic removal of a directing group is reported, complementing the currently exclusively used nucleophilic strategy. Rh(III)-catalyzed, N-nitroso-directed C-H activation allows the development of a traceless, atom- and step-economic, cascade approach for the synthesis of indole skeletons, starting from readily available N-nitroso and α-diazo-β-keto compounds. Importantly, the cyclization/denitrosation reaction represents a hitherto unobserved reactivity pattern for the N-nitroso group.

An efficient double C-N bond formation sequence to prepare highly substituted quinazolines utilizing benzimidates and dioxazolones under the catalytic redox-neutral [Cp*RhCl2]2/AgBF4 system, where dioxazolones could work as an internal oxidant to maintain the catalytic cycle, is reported. N-Unsubstituted imine not only acts as a directing group but also functions as a nucleophile in postcoupling cyclization, and dioxazolone acts as a coupling partner for access to heterocycle.

Despite their tremendous synthetic and pharmaceutical utility, primary azaaromatic amines remain elusive for access based on a generally applicable C-H functionalization strategy. An oxadiazolone-enabled approach is reported for convenient entry into N-unsubstituted 1-aminoisoquinolines through Co(III)-catalyzed redox-neutral, step-, atom-, and purification-economic C-H functionalization with alkynes. A N labeling experiment reveals the effectiveness of both oxadiazolone N atoms as directing sites. The installed primary amine can be harnessed as a synthetically useful handle for attachment of divergent appendages.