Synthesis of Cyclopropyl Carbocyclic Purine Nucleosides via Base-Promoted [2 + 1] Annulation of Alkenyl Sulfonium Salts.

We herein report a facile and efficient base-promoted annulation approach to construct cyclopropyl carbocyclic purine nucleoside analogues. Using α-purine-substituted acetones/acetophenones as challenging dinucleophiles, this reaction undergoes selective C/C nucleophilic attack to achieve [2 + 1] annulation with alkenyl sulfonium salts (up to 92% yield, 24 examples). This reaction employs safer and more readily available starting materials, proceeds under transition-metal-free and mild conditions, and possesses broad functional group tolerance, thus showing great potential for practical applications in nucleoside chemistry.