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Metallo Protic N-Allyl Enammonium Ylide 3-Aza-Cope Rearrangement Enabled by Resonance-Assisted H-Bonding: Direct

Laxman Anandrao Thorbole¹, Sudhir Muduli¹, Sreenivas Katukojvala¹

¹Department of Chemistry, Indian Institute of Science Education & Research Bhopal, Madhya Pradesh 462066, India.

Organic Letters

|April 9, 2026

Abstract

None:

The 1,2-proton transfer reactions of high-energy metal-bound protic ammonium ylides have received significant attention in NH-insertion reactions. However, their sigmatropic reactions remain challenging due to rapid protodemetalation. Herein, we have designed a conceptually new class of Rh-bound protic N-allyl enammonium ylides for stereoselective 3-aza-Cope rearrangement. These transient ylides are generated in situ by the Rh-catalyzed reaction of vinyldiazo compounds and secondary (Z)-β-enamino carbonyl compounds under mild conditions. Mechanistic studies revealed that resonance-assisted hydrogen bonding (RAHB) promotes [3,3] rearrangement by disfavoring 1,2-proton transfer or direct C-C bond formation. The methodology enables direct synthesis of functionalized 4-vinylpyrroles and deuterated pyrroles. The pyrrole products were elaborated to the 7-arylindole and valuable tricyclic pyrroloindoline scaffold of a novel antitumor and UV-A-protecting agent, terreusinone.

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