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

Abstract

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.

Complexes Bearing Protic N-Heterocyclic Carbenes: Synthesis and Applications

“…-allyltheophylline 57, can be oxidatively added to low-valent group 10 metals (Scheme 24). 61,62 Reaction of 8-chlorocaffeine with [M(PPh 3 ) 4 ] (M = Pd and Pt) in the absence of a proton source yields the platinum complex [58] or the palladium complex [59] possessing a caffeine-derived anionic ylidene ligand. In the presence of a proton source, the cationic complexes [61] and [62] have been obtained from the same reaction.…”

“…61,62 Reaction of 8-chlorocaffeine with [M(PPh 3 ) 4 ] (M = Pd and Pt) in the absence of a proton source yields the platinum complex [58] or the palladium complex [59] possessing a caffeine-derived anionic ylidene ligand. In the presence of a proton source, the cationic complexes [61] and [62] have been obtained from the same reaction. These complexes can also be obtained by the protonation of [58] and [59] using HBF 4 .…”

Synthese von Komplexen mit anomalen “protischen” N‐heterocyclischen Carbenen

“…[16] Die letztgenannte Methode ermçglicht auch die problemlose C8-Metallierung von Biomolekülen wie Koffein oder Adenin. [17] Komplexe mit den dazu verwandten protischen aNHC-Liganden wie F (mit einem protonierten Ring-Stickstoffatom und einem C2-Proton) waren bisher nicht bekannt. Bei unseren Versuchen, derartige Komplexe erstmals zu synthetisieren, haben wir die oxidative Addition von 4-Halogen-N-alkylazolen an Pt 0 -Komplexe untersucht.…”

Nucleobases Having M–C Bonds: An Emerging Bio‐Organometallic Field

“…[14] The reactions were carried out with a range of alkynes, in methanol, at room temperature, and led to the M-C alkyne insertion products (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) in good to excellent yields, regardless the nature of the metal [Ir III or Rh III ]. [14] The reactions were carried out with a range of alkynes, in methanol, at room temperature, and led to the M-C alkyne insertion products (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) in good to excellent yields, regardless the nature of the metal [Ir III or Rh III ].…”

“…[25] The authors prepared C8-halogenated purine derivatives and reacted them with [Pt(PPh 3 ) 4 ]. [25] The authors prepared C8-halogenated purine derivatives and reacted them with [Pt(PPh 3 ) 4 ].…”