Synthesis of cyclic sulfides
With CuI as the catalyst and K3PO4 • 3 H2O as the base, a highly efficient, ligand-free intramolecular S-vinylation of thiols with vinyl chlorides or bromides was successfully implemented. Moreover, competition experiments revealed that the 4-exo cyclization is fundamentally preferred over other modes (5-exo, 6-exo, and 6-endo) of cyclization.
Q. Zhao, L. Li, Y. Fang, D. Sun, C. Li, J. Org. Chem., 2009, 74, 459-462.