Bulletin of the Korean Chemical Society

Korean Chemical Society (대한화학회)
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Synthesis of N-Alkylated 4-Fluoro-5-phenylpyrrole-2-carboxylate via Isolable Pyrroline Ionic Intermediates

  • Kim, Sung-Kwan (Department of Bionanochemistry, Wonkwang University) ;
  • Jun, Chang-Soo (Department of Bionanochemistry, Wonkwang University) ;
  • Kwak, Kyung-Chell (Department of Bionanochemistry, Wonkwang University) ;
  • Park, Kwang-Yong (School of Chemical Engineering and Material Science, Chung-Ang University) ;
  • Chai, Kyu-Yun (Department of Bionanochemistry, Wonkwang University)
  • Published : 2007.12.20
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Abstract

Organic fluorine chemistry produces many useful products. This paper elucidates the reaction of ethyl-4,4- difluoro-2-iodo-5-oxo-5-phenylpentanoate (2) with primary amines in a one-pot scheme. The reaction produced a series of β-fluoropyrrole derivatives at ambient temperatures. In this reaction, the less bulky the primary amine the higher was the resultant yield. When (2) and aqueous methylamine (40%) were allowed to react below 0 oC, 5-(ethoxycarboxyl)-1-methyl-3,3-difluoro-2-hydroxy-2-phenylpyrrolidine, an intermediate molecule for 2-ethyl-4-flouro-1-methyl-5-phenylpyrrole-2-carboxylate (5), was isolated first. Then, (5) reacted with hydroperchloric acid and acetic anhydride to form 5-(ethoxycarboxyl)-1-methyl-3,3-difluoro-2- phenylpyrrolinium perchlorate (6), which was converted to 2-ethyl-4-flouro-1-methyl-5-phenylpyrrole-2- carboxylate gradually in the presence of a base. Our experiments demonstrate that the formation of 2-ethyl-4- flouro-1-methyl-5-phenylpyrrole-2-carboxylate occurs via both one-pot schemes and stepwise pathways, depending on the reaction conditions. The isolation and characterization of the isolated intermediate (6) suggest an anionic pathway for this reaction.

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References

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