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1 2004

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Synthesis of Fluorinated Dialkyl 1-Aryl-4-alkoxy-5-oxo-2,5-dihydro-1H-pyrrole-2,3-dicarboxylates

Yavari I., Nasiri F., Djahaniani H.

Polish Journal of Chemistry

2004

Vol. 78 / nr 10

1871-1876

Alkyl 2-(2-fluoro-anilino)-2-oxo-acetates or ethyl 2-oxo-2-(trifluoromethylanilino)-acetate undergo a multistep reaction with dialkyl acetylenedicarboxylates in the presence of triphenylphosphine to produce dialkyl l-(2-fluorophenyl)-4-alkoxy-5-oxo-2,5-dihydro-1H-pyrrole-2,3-dicarboxylates or dialkyl 4-ethoxy-5-oxo-1-[2-(trifluoromethyl)-phenyl]-2,5-dihydro-1H-pyrrole-2,3-dicarboxylates in good yields. Dynamic NMR study of dimethyl 4-ethoxy-5-oxo-1-[2-(trifluoromethyl)-phenyl]-2,5-dihydro-1H-pyrrole- 2,3-dicarboxylate shows a fairly high energy barrier (DeltaG _ = 60.9 kJ mol-1) for rotation around the N-aryl single bond, which leads to an observable atropisomerism.