Study of aromatic nucleophilic substitution with amines on nitrothiophenes in room-temperature ionic liquids: are the different effects on the behavior of para-like and ortho-like isomers on going from conventional solvents to room-temperature ionic liquids related to solvation effects?

J Org Chem. 2006 Jul 7;71(14):5144-50. doi: 10.1021/jo060435q.

Abstract

The kinetics of the nucleophilic aromatic substitution of some 2-L-5-nitrothiophenes (para-like isomers) with three different amines (pyrrolidine, piperidine, and morpholine) were studied in three room-temperature ionic liquids ([bmim][BF4], [bmim][PF6], and [bm(2)im][BF4], where bmim = 1-butyl-3-methylimidazolium and bm(2)im = 1-butyl-2,3-dimethylimidazolium). To calculate thermodynamic parameters, a useful instrument to gain information concerning reagent-solvent interactions, the reaction was carried out over the temperature range 293-313 K. The reaction occurs faster in ionic liquids than in conventional solvents (methanol, benzene), a dependence of rate constants on amine concentration similar to that observed in methanol, suggesting a parallel behavior. The above reaction also was studied with 2-bromo-3-nitrothiophene, an ortho-like derivative able to give peculiar intramolecular interactions in the transition state, which are strongly affected by the reaction medium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amines / chemistry*
  • Borates / chemistry
  • Imidazoles / chemistry
  • Ionic Liquids / chemistry*
  • Kinetics
  • Molecular Structure
  • Solubility
  • Solvents / chemistry
  • Stereoisomerism
  • Temperature*
  • Thiophenes / chemical synthesis
  • Thiophenes / chemistry*

Substances

  • 1-butyl-3-methylimidazolium tetrafluoroborate
  • 2-bromo-3-nitrothiophene
  • Amines
  • Borates
  • Imidazoles
  • Ionic Liquids
  • Solvents
  • Thiophenes