Rhodium(III)-Catalyzed Redox-Neutral [4 + 2] Annulation of 3,5-Diaryloxadiazoles with Alkynes: A Dual C–H Activation Strategy for Constructing C–N Atropisomers

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A rhodium(III)-catalyzed dual-ring formation via cascade C-H activation/[4 + 2] annulation of 3,5-diaryoxadiazoles with alkynes was developed. This strategy has been demonstrated with a variety of 3,5-diaryloxadiazoles and alkynes, and it has been successfully scaled up to gram-scale synthesis, highlighting its potential significance in the direct construction of C-N atropisomers. Furthermore, the cleavage of the N-O bond is essential for the formation of the bicyclic structure in the absence of an external oxidant. Mechanistic studies revealed that cleavage of the C-H bond at the 3-phenyl group of oxadiazole was likely a rate-determining step in this reaction.