A general method for the direct formation of dihydroazepine derivatives from 1-sulfonyl-1,2,3-triazoles possessing a tethered diene is reported. Mechanistic investigations performed suggest that the process involves an intramolecular cyclopropanation of a a-imino Rh-carbenoid species, leading to a transient 1-imino-2-vinylcyclopropane intermediate which rapidly undergoes a 1-aza-Cope rearrangement to generate fused dihydroazepine derivatives, in good yields. The resulting products were shown to be useful synthetic intermediates in a variety of transformations, leading to a diverse array of bicyclic heterocycles.

Expedient synthesis of fused azepine derivatives via a tandem Rh(II)-catalyzed cyclopropanation/1-aza-Cope rearrangement of dienyltriazoles

248th National Meeting (2014)

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