An Umpolung Strategy for Palladium-Catalyzed Dearomative Allylation toward Eight-Membered N-Heterocycles

In this study, umpolung palladium catalysis was developed for achieving 1,2-dearomative allylation followed by intramolecular cyclization. The dearomatization involves activated N-arenes and the in situ generated nucleophilic η¹-allyl-palladium species from a bis-allyl precursor, efficiently affording eight-membered heterocycles with potential bioactivity─structures that are otherwise difficult to access. The synthetic utility of this methodology was further demonstrated through versatile transformations of the heterocyclic products, enabling the construction of complex molecular architectures. Mechanistic studies revealed a regioselective dearomatization pathway involving η¹-allyl-palladium, which was kinetically favored over alternative dearomatizations. These findings could expand the practical scope of umpolung palladium catalysis in organic synthesis.