Aliphatic thiols are contaminants generated during refining of crude oil, and are not generally converted into useful compunds. Vinyl sulfides (pictured) are promising building blocks for sulfur-functionalized polymers, but their synthesis from branched thiols has so far been challenging.
Valentine P. Ananikov, Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, and colleagues have developed a palladium-catalyzed synthesis converting primary, secondary, and even tertiary thiols into the corresponding Markovnikov-type vinyl sulfides. The readily available N-heterocyclic carbene complex (NHC)Pd(acac)Cl efficiently catalyzed the addition of a wide range of aliphatic, benzylic, and aromatic thiols to alkynes, yielding the desired vinyl sulfides.
The reactions showed high selectivities and good to excellent yields. The researchers propose that the catalytic cycle proceeds via coordination of sulfur to the palladium center and subsequent insertion of the alkyne into the Pd–S bond.
- Pd-NHC Catalytic System for the Efficient Atom-Economic Synthesis of Vinyl Sulfides from Tertiary, Secondary, or Primary Thiols,
Evgeniya S. Degtyareva, Julia V. Burykina, Artem N. Fakhrutdinov, Evgeniy G. Gordeev, Victor N. Khrustalev, Valentine P. Ananikov,
ACS Catal. 2015.