The first rhodium-catalyzed anti-markovnikov hydroamination: Studies on hydroamination and oxidative amination of aromatic olefins

M. Beller, H. Trauthwein, M. Eichberger, C. Breindl, J. Herwig, T. E. Müller, O. R. Thiel

Research output: Contribution to journalArticlepeer-review

180 Scopus citations

Abstract

The first transition-metal-catalyzed regiospecific anti-Markovnikov hydroamination of aromatic olefins is reported. Styrene and substituted styrenes react with secondary aliphatic amines, especially morpholine and Narylpiperazines, in the presence of cationic rhodium complexes to give 2- aminoethenylbenzene and 2-aminoethylbenzene derivatives. Cationic [Rh(cod)2]+BF4- and various phosphines (l:2-mixture) were employed as in situ catalysts. According to labeling experiments, there is no evidence that the hydroamination is a consecutive hydrogenation of a previously formed enamine. Hydroamination with simple secondary amines, for example piperidine, can also be achieved by the use of a higher olefin concentration and higher reaction temperatures than those given in previously published reaction procedures. Kinetic investigations of the major reaction pathway reveal that the reaction rate of the oxidative amination and the hydroamination is dependent on the styrene and on the catalyst concentration, and independent of the amine concentration. Experiments that employed deuterium-labeled amines (N-D) provided evidence that the mechanism involves an amine- activating pathway. The substituents on the styrene, the phosphine ligand, and the solvent influence the yield of the aminations and the enamine:alkylamine ratio.

Original languageEnglish
Pages (from-to)1306-1319
Number of pages14
JournalChemistry - A European Journal
Volume5
Issue number4
DOIs
StatePublished - 1999
Externally publishedYes

Keywords

  • Aminations
  • Anti-Markovnikov reaction
  • Catalysts
  • Reaction mechanism
  • Rhodium complexes

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