Synthesis of Fluorinated Heteroaromatics by [3+2] Cycloaddition of N-Oxides with Hexafluoropropene

Significance

Reported is the synthesis of fluorinated heteroaromatic esters, thioesters, and amides from the reaction of hexafluoropropene with the corresponding N-oxides. Previously reported work by the Makosza group showed that this reaction is useful for the preparation of highly fluorinated alkyl pyridines. The reaction proceeds via the expected [3+2] cycloaddition to 1 followed by fragmentation to the acyl fluoride 2 which undergoes reaction with nucleophiles to give products 3. In the case of formation of carboxylic acid 3, R² = OH, spontaneous decarboxylation occurs to give the previously reported fluorinated alkyl pyridines.