A Versatile Methodology for the Regioselective C8-Metalation of Purine Bases

Purine nucleobases are excellent ligands for metal ions, forming normally coordinative Werner-type bonds by utilizing the N donor atoms of the nucleobase skeleton. Here we show that purines such as 8-chlorocaffeine and 8-bromo-9-methyladenine react with [Pt(PPh3)(4)] under oxidative addition of the C-8-halogen bond to the metal center. The resulting Pt-II complexes feature a C-8-bound ylidene ligand. Protonation of the ylidene at the N-7/9-atom yields complexes bearing a protic N-heterocyclic carbene ligand derived from the purine base with an NMe,NH-substitution pattern.