Site-selective direct arylation of unprotected adenine nucleosides mediated by palladium and copper: insights into the reaction mechanism

Thomas E. Storr, Andrew G. Firth, Karen Wilson, Kate Darley, Christoph G. Baumann, Ian J.S. Fairlamb

Research output: Contribution to journalArticle

Abstract

Reaction conditions facilitating the site-selective direct aryl functionalisation at the C-8 position of adenine nucleosides have been identified. Many different aromatic components may be effectively cross-coupled to provide a diverse array of arylated adenine nucleoside products without the need for ribose or adenine protecting groups. The optimal palladium catalyst loading lies between 0.5 and 5 mol %. Addition of excess mercury to the reaction had a negligible affect on catalysis, suggesting the involvement of a homogeneous catalytic species. A study by transmission electron microscopy (TEM) shows that metal containing nanoparticles, ca. 3 nm with good uniformity, are formed during the latter stages of the reaction. Stabilised PVP palladium colloids (PVP=N-polyvinylpyrrolidone) are catalytically active in the direct arylation process, releasing homogenous palladium into solution. The effect of various substituted 2-pyridine ligand additives has been investigated. A mechanism for the site-selective arylation of adenosine is proposed.
Original languageEnglish
Pages (from-to)6125-6137
Number of pages13
JournalTetrahedron
Volume64
Issue number26
Early online date18 Jan 2008
DOIs
Publication statusPublished - 23 Jun 2008

Keywords

  • direct arylation
  • purines
  • C–C Bond formation
  • palladium
  • copper(I) salts

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