Synthesis of Pd<sup>II</sup> Complexes Bearing <i>p</i>NHC Ligands by Oxidative Addition of 8-Halogenotheophyllines and 8-Bromoadenine to Pd<sup>0</sup>
Jonas Blumenberg, Lukas F. B. Wilm, F. Ekkehardt Hahn
Abstract
Various 8-halogenotheophyllines (halogen = Cl, Br, I) were selectively C8 metalated by an oxidative addition of the C8–halogen bond to [Pd(PPh3)4] to give the PdII azolato complexes [1]–[3]. The complexes were protonated at the N9 nitrogen atom to yield the NH,NH-NHC (pNHC) complexes [4]BF4–[6]BF4. Due to the unsymmetrical nature of the backbone of the theophylline-derived pNHC ligands, two NH resonances were observed by 1H NMR spectroscopy. In addition, 8-bromoadenine was also regioselectively C8 metalated via an oxidative addition of the C8–Br bond to [Pd(PPh3)4] in the presence of the proton source pyridinium tetrafluoroborate to give [7]BF4.
Topics & Concepts
ChemistryOxidative additionPyridiniumProtonationMedicinal chemistryHalogenTetrafluoroborateYield (engineering)Reductive eliminationNuclear magnetic resonance spectroscopyPalladiumStereochemistryCatalysisIonOrganic chemistryIonic liquidMaterials scienceMetallurgyAlkylN-Heterocyclic Carbenes in Organic and Inorganic ChemistryCatalytic Cross-Coupling ReactionsCatalytic C–H Functionalization Methods