Single-carbon-atom transfer to para-quinone methides from TMSCF₂Br

Single-carbon-atom transfer reactions offer a powerful strategy for constructing complex molecular architectures by sequential assembly of substituents around the atomic carbon core. However, the limited availability of atomic carbon sources has significantly hindered progress in this field. Herein, we demonstrate a single-carbon atom transfer reaction utilizing commercially available TMSCF₂Br as an atomic carbon equivalent. Through a cascade of 1,6-addition and TBAF-catalyzed intramolecular cyclization with para-quinone methides (p-QMs), gem-difluorinated spiro[2.5]octa-4,7-dien-6-ones were efficiently formed. These spirocyclic intermediates exhibit remarkable electrophilicity, enabling stereoselective capture of diverse nucleophiles to access fluorinated alkenes with excellent stereocontrol. The resulting fluoroalkenes serve as versatile platforms for constructing tetrasubstituted alkenes via nucleophilic vinylic substitution (S_NV), achieving excellent stereoselectivities. In the presence of a 1,3-bisnucleophile, for example a C2-substituted acetoacetate ester, cyclic 2-methylene-2,3-dihydrofuran was generated via a sequential S_NV reaction with excellent stereoselectivities. Moreover, a computational study and a control experiment provide insight into the mechanism of the reaction.