Palladium-catalyzed direct arylation of 5-halouracils and 5-halouracil nucleosides with arenes and heteroarenes promoted by TBAF

J Org Chem. 2014 May 2;79(9):4094-103. doi: 10.1021/jo500602p. Epub 2014 Apr 23.

Abstract

The 1-N-benzyl-5-iodo(or bromo)uracil undergoes Pd-catalyzed [Pd2(dba)3] direct arylation with benzene and other simple arenes in the presence of TBAF in DMF without the necessity of adding any ligands or additives to give 5-arylated uracil analogues. The TBAF-promoted coupling also occurs efficiently with electron rich heteroarenes at 100 °C (1 h) even with only small excess of heteroarenes. The protocol avoids usage of the arylboronic acid or stannane precursors for the synthesis of 5-(2-furyl, or 2-thienyl, or 2-pyrrolyl)uracil nucleosides, which are used as important RNA and DNA fluorescent probes. The fact that 1-N-benzyl-3-N-methyl-5-iodouracil did not undergo the TBAF-promoted couplings with arenes or heteroarenes suggests that the C4-alkoxide (enol form of uracil) facilitates coupling by participation in the intramolecular processes of hydrogen abstraction from arenes. TBAF-promoted arylation was extended into the other enolizable heterocyclic systems such as 3-bromo-2-pyridone. The π-excessive heteroarenes also coupled with 5-halouracils in the presence of Pd(OAc)2/Cs2CO3/PivOH combination in DMF (100 °C, 2 h) to yield 5-arylated uracils.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzene Derivatives / chemical synthesis
  • Benzene Derivatives / chemistry*
  • Catalysis
  • Molecular Structure
  • Nucleosides / chemistry*
  • Palladium / chemistry*
  • Quaternary Ammonium Compounds / chemistry*
  • Uracil / analogs & derivatives
  • Uracil / chemistry*

Substances

  • Benzene Derivatives
  • Nucleosides
  • Quaternary Ammonium Compounds
  • Uracil
  • Palladium
  • tetrabutylammonium