Au(I)-catalyzed and iodine-mediated cyclization of enynylpyrazoles to provide pyrazolo[1,5-a]pyridines

Org Biomol Chem. 2012 Sep 7;10(33):6640-8. doi: 10.1039/c2ob25973g. Epub 2012 Jul 23.

Abstract

Pyrazolo[1,5-a]pyridines and 6-iodopyrazolo[1,5-a]pyridines were synthesized by gold-catalyzed and iodine-mediated cyclization of enynylpyrazoles in good to excellent yields, respectively. The iodinated adducts were further converted to 6-arylpyrazolo[1,5-a]pyridines via Suzuki-Miyaura coupling reaction and 6-cyanopyrazolo[1,5-a]pyridine by Ullmann condensation reaction. One of the cyclization adducts, 2-(4-fluorophenyl)pyrazolo[1,5-a]pyridine, was converted to a p38 kinase inhibitor, 2-(4-fluorophenyl)-3-(4-pyridinyl)pyrazolo[1,5-a]pyridine, in two steps.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalysis
  • Cyclization
  • Gold / chemistry*
  • Halogenation
  • Iodine / chemistry*
  • Pyrazoles / chemical synthesis*
  • Pyrazoles / chemistry
  • Pyridines / chemical synthesis*
  • Pyridines / chemistry

Substances

  • Pyrazoles
  • Pyridines
  • pyrazolo(3,4-b)pyridine
  • Gold
  • Iodine