Dirhodium-imidyl reactive intermediates generated in situ from N-tosyloximes in CH2Cl2 at rt were exploited in three unusual synthetic applications: (1) desaturative annulation, a biomimetic C-C ring-closure between 1,3-methylenes with loss of two hydrogens; (2) directed desaturation, a regioselective, acceptorless olefination via β-hydride elimination; and (3) C-H functionalizations using an exceptionally broad variety of inorganic and organic nucleophiles including several unconventional examples, e.g., F-, ethers, and acyl silanes. The remarkable variety and regiocontrol of these directed transformations are attributed to a cyclic Rh2-mediated C-H activation mechanism that contrasts sharply with typical imidyl 1,5-hydrogen atom transfer (1,5-HAT) processes. Substrate scope includes benzylic, allylic, propargylic, tertiary, and α-alkyloxy centers.

Remote Rh C-H activation: Desaturative annulation, directed desaturation, and C-H functionalization

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