19117-20-5Relevant articles and documents
Pyridine-assisted chlorinations and oxidations by palladium(IV)
McCall, A. Scott,Kraft, Stefan
scheme or table, p. 3527 - 3538 (2012/06/16)
The reactivity of the bis-NHC complex LPdIVCl4 (L = κ2-[R-NHCCH2NHC-R] with R = C14H 29) in chlorinations and oxidations of organic substrates was considerably increased in the presence of pyridine. For alkene chlorinations, this effect was due to the in situ formation of highly reactive LPd IVCl3(py)+, which was able to transfer Cl + to the C=C bond in a ligand-mediated process (devoid of π complexation), which did not require py dissociation. The enhanced reactivity in the presence of pyridine also extended to the oxidation of secondary and benzylic alcohols under mild conditions in a reaction where py served as a base, broadening the known scope of reactivity for PdIV complexes. LPdIVCl3(py)+ could be formed from Cl -/py exchange or from the oxidation of LPdIICl(py) + by Cl2. Taking advantage of the enhanced reactivities that pyridine coordination imparted on both PdII and PdIV complexes allowed for the catalytic chlorination of styrene with LPd IVCl4 as a sacrificial oxidant, thereby establishing the principal feasibility of PdII/PdIV catalyses that obviates PdII activations of the substrate.
