Metallation reactions. XXI. Metallation of alkyl (alkylthio) benzenes by superbases versus organolithium compounds

Article abstract of DOI:10.1016/S0040-4020(01)90456-9

The metallation regiochemistry of alkyl(alkylthio)benzenes with butyllithium or with the superbasic mixture of butyllithium with potassium tert-butoxide is described. The reaction pattern depends on the substrate and the reagent. Butyllithium monometallates the thiomethylic carbon of methyl (methylthio) benzenes and bimetallates the thiomethylic and the annular carbon ortho to the thioethereal group. With superbases the metallation occurs at the thiomethylic and methylic carbon. Metallation with butyllithium of the higher homologs substitutes exclusively the hydrogen ortho to the thioalkylic group, while the superbases attack also the carbon atom alpha to the thioalkyl substituent.