Deprotonative magnesation and cadmation of [1,2,3]triazolo[1,5-a]pyridines

J Org Chem. 2009 Jan 2;74(1):163-9. doi: 10.1021/jo801675h.

Abstract

[1,2,3]Triazolo[1,5-a]pyridine and 3-substituted derivatives were regioselectively metalated at the 7 position using either Bu3MgLi or (TMP)3CdLi, the former at -10 degrees C and the latter at room temperature. The lithium arylmagnesates (R = H, Me, Ph) proved to react with iodine (34-75%) or 3,4,5-trimethoxybenzaldehyde (32-51%). Attempts to obtain the cross-coupling products using 2-bromopyridine under palladium catalysis failed, a result attributed to the low stability of these compounds. The corresponding lithium arylzincates reacted in 17-60% yield under the same reaction conditions. The lithium arylcadmates were either trapped with iodine (38-76%, R = H, Me, Ph, CN, 2-thienyl) or involved in palladium-catalyzed cross-coupling reactions with 2-bromopyridine (26-67%, R = H, Me, Ph). For R = 2-pyridyl, 3-(6-iodo-2-pyridyl)-[1,2,3]triazolo[1,5-a]pyridine was isolated in 73% yield. (TMP)3CdLi also proved suitable for the clean dideprotonation of two substrates (R = H, 2-thienyl), a result demonstrated by quenching with iodine (66-75%).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cadmium / chemistry*
  • Lithium / chemistry*
  • Magnesium / chemistry*
  • Molecular Structure
  • Organometallic Compounds / chemistry*
  • Protons*
  • Pyridines / chemistry*
  • Stereoisomerism
  • Triazoles / chemistry*

Substances

  • Organometallic Compounds
  • Protons
  • Pyridines
  • Triazoles
  • Cadmium
  • Lithium
  • Magnesium