Divergent and regioselective synthesis of 1,2,4- and 1,2,5-trisubstituted imidazoles

J Org Chem. 2008 Sep 5;73(17):6816-23. doi: 10.1021/jo801256b. Epub 2008 Aug 6.

Abstract

A divergent and regioselective synthesis of 1,2,4- and 1,2,5-trisubstituted imidazoles from a readily available (two steps) common intermediate has been developed. This methodology is based on the regiocontrolled N-alkylation of 1-(N,N-dimethylsulfamoyl)-5-iodo-2-phenylthio-1H-imidazole (10). When this intermediate is engaged in reaction with methyl triflate, selective formation of the corresponding 1,2,5-trisubsituted 1H-imidazole is observed. NMR studies have revealed that this regioselectivity can be accounted for by in situ rapid isomerization of 10 into its 1,2,4-isomer (13) followed by regiospecific N-alkylation of the latter. Conversely, when key intermediate 10 is slowly added to Meerwein's salt, isomerization can be constrained and regiospecific N-alkylation of 10 leads to 1,2,4-trisubstituted 1H-imidazole with a high selectivity. The general character of this methodology has been illustrated by showing that iodine in position 4 or 5 could be easily substituted by an aryl group by Suzuki coupling, whereas the phenylthio group at position 2 could, after oxidation into sulfone, be displaced by nucleophilic substitution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkylation
  • Hydrocarbons, Iodinated / chemistry*
  • Imidazoles / chemical synthesis*
  • Isomerism
  • Magnetic Resonance Spectroscopy
  • Models, Chemical
  • Oxidation-Reduction
  • Sulfhydryl Compounds / chemistry*
  • Sulfonamides / chemistry*
  • Sulfones / chemistry

Substances

  • Hydrocarbons, Iodinated
  • Imidazoles
  • Sulfhydryl Compounds
  • Sulfonamides
  • Sulfones