Cationic palladium(ii)-catalyzed dehydrative nucleophilic substitutions of benzhydryl alcohols with electron-deficient benzenethiols in water

Abstract

An efficient direct nucleophilic substitution of benzhydryl alcohols with electron-deficient benzenethiols using cationic Pd(II) catalysts as Lewis acids in water is reported. Atom economical and environmentally benign protocols afford S-benzylated products in moderate to excellent yields. Commercially available Pd(MeCN)₄(OTf)₂, PdCl₂(MeCN)₂, and Na₂PdCl₄ are highly efficient catalysts. Notably, this simple protocol can be achieved without any other additives such as acids, bases, or external ligands. A Hammett study on the rate constants of S-benzylation by using various substituted benzhydryl alcohols yielded negative ρ values, suggesting that there is a build-up of positive charge in the transition state.