Synthesis of Fluoropyridines from 4-(2-Fluoroallyl)oxazolones

Significance

The synthesis of polysubstituted 4-fluoropyridines from fluorinated amino acid allylic esters involving successive Ireland-Claisen (A) and aza-Cope (B) rearrangements of oxazolone derivatives in modest yields is reported. None of the intermediates suggested in the mechanism shown could be isolated although an analogous species to the carbene (C) has been trapped with dimethyl acetylenedicarboxylate (J. Fischer, W. Steglich Angew. Chem., Int. Ed. Engl. 1979, 18, 167-168). 4-Methyl oxazolones do not lead to fluoropyridine derivatives.