Interrogation of a Sonogashira Cross-Coupling of 8-Bromoguanosine with Phenylacetylene on Amberlite: Evidence for Pd/Cu Ion Binding and Propagation of Pd/Cu Nanoparticles

• Published in: Nucleosides, nucleotides & nucleic acids nucleotides & nucleic acids, 2011-02, Vol.30 (2), p.168-184
• Main Authors: Firth, Andrew G., Wilson, Karen, Baumann, Christoph G., Fairlamb, Ian J. S.
• Format: Article
• Language: English
• Subjects: Acetylene - analogs & derivatives; Acetylene - chemistry; alkyne; Binding Sites; catalyst recycling; Copper - chemistry; cross-coupling; Guanosine - analogs & derivatives; Guanosine - chemistry; inhibition; Nanoparticles - chemistry; Nucleoside; Organometallic Compounds - chemical synthesis; Organometallic Compounds - chemistry; palladium; Palladium - chemistry; Particle Size; Resins, Synthetic - chemistry; Surface Properties
• ISSN: 1525-7770; 1532-2335
• DOI: 10.1080/15257770.2010.548844

The reactivity of Amberlite (IRA-67) base "heterogeneous" resin in Sonogashira cross-coupling of 8-bromoguanosine 1 with phenylacetylene 3 to give 2 has been examined. Both 1 and 2 coordinate to Pd and Cu ions, which explains why at equivalent catalyst loadings, the homogeneous reaction employing triethylamine base is poor yielding. X-ray photo-electron spectroscopy (XPS) has been used to probe and quantify the active nitrogen base sites of the Amberlite resin, and postreaction Pd and Cu species. The PdCl 2 (PPh 3 ) 2 precatalyst and CuI cocatalyst degrade to give Amberlite-supported metal nanoparticles (average size ∼2.7 nm). The guanosine product 2 formed using the Amberlite Pd/Cu catalyst system is of higher purity than reactions using a homogeneous Pd precatalyst, a prerequisite for use in biological applications.