Harnessing Vinyl Cation Reactivity Enables Oxime Ether Formation and an Unusual Base-Promoted Rearrangement to Esters

Harnessing vinyl cation reactivity under controlled conditions remains a longstanding challenge in carbocation chemistry, as the ionization of vinyl triflates and related precursors is often slow, limiting the development of general and selective reaction manifolds involving vinyl cations. Here, we report an aluminum-catalyzed strategy that generates and intercepts vinyl cation intermediates from vinyl triflates, enabling direct access to oxime ethers using readily available nitroalkanes. Oxime ether formation often exhibits a pronounced Z selectivity (up to Z/E = 93:7, depending on the substrate), affording geometrically defined products. Mechanistic studies supported by DFT calculations suggest the intermediacy of an N-oxomethaniminium species, revealing a previously unrecognized reactivity pathway. In addition to oxime ether formation, these intermediates undergo a base-promoted rearrangement to esters, enabling a base-gated tandem transformation directly from vinyl triflates. A broad substrate scope (64 examples) demonstrates the robustness of this vinyl cation platform and provides unified access to defined oxime ethers and esters.