Barton-Zard Reaction of β-Fluoro-β-nitrostyrenes─a Selective Route to Functionalized 4-Fluoropyrroles.

The Barton-Zard reaction of β-fluoro-β-nitrostyrenes with ethyl α-isocyanoacetate was studied. The reaction was found to proceed in a highly chemoselective manner to form preferably 4-fluoropyrroles in up to 77% yield. The corresponding 4-nitrosubstituted pyrroles are formed as minor products of the reaction. The broad scope of β-fluoro-β-nitrostyrenes was demonstrated in the preparation of a variety of fluorinated pyrroles. The obtained experimental results are in perfect agreement with the data obtained by theoretical investigation of this reaction. The subsequent study of synthetic utility of monofluorinated pyrroles was performed to open a way for the development of a variety of functionalized pyrrole derivatives.