Glycerol as a Recyclable Solvent for Copper-Mediated Ligand-Free C-S Cross-Coupling Reaction: Application to Synthesis of Gemmacin Precursor

A highly efficient copper catalyzed ligand-free C-S cross-coupling reaction of aryl halides with thiols has been performed in the presence of environmentally benign solvent glycerol. A variety of aryl thiols are prepared with good chemoselectivity and functional group tolerance. The catalytic system is found to be active for more challenging and less reactive aryl bromides. The catalyst and solvent are recyclable up to five cycles. The developed methodology is used for the synthesis of a sulfide precursor of Gemmacin B and Gemmacin antibiotics.