Decarboxylative-Derived 2-Aminoallyl Cations in Copper-Catalyzed Spirocyclization of Naphthols and Indoles

The dearomatization reactions of indoles or naphthols with 2-aminoallyl cations generated from ethynyl methylene carbamates (EMCCs) for the concise synthesis of spirocyclic compounds represent a significant challenge. This difficulty stems from the substantial energy barrier associated with the initial disruption of aromaticity. Nonetheless, a diverse array of spirocyclic compounds can be prepared in moderate to good yields (69-92%) under mild reaction conditions. This synthetic protocol exhibits notable advantages, including a broad substrate scope, excellent functional group tolerance, and simple operational procedures. Furthermore, scale-up experiments and late-stage functionalization studies have further underscored the practical synthetic value of this methodology. Finally, in terms of the reaction mechanism, besides the cyclization reaction, it also involves a 1,5-hydrogen shift, which constructs an unexpected cyclized compound structure and enhances the interest of the research.