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A novel method of the preparation of (hetero)aryl nitriles based on the fragmentation of the corresponding pentafluorophenylhydrazones is described. The synthesis is metal‐free, proceeds in neutral conditions with no need of protecting group application and provides most nitriles in moderately good yields. The synthesis was performed on ten pentafluorophenylhydrazones with different functional groups within the carbonyl part – the reaction was found to be partially substrate selective. The reaction prefers substrates with aromatic electron donating substituents on the carbonyl part of the hydrazone. The second reaction product, 2,3,5,6‐tetrafluoroaniline, can be easily separated by vacuum distillation. Although the reaction mechanism is yet to be ascertained, all synthetic and spectroscopic data suggest a radical reaction mechanism.

Activated enol ethers derived from methyl or ethyl acetoacetate/cyanoacetates or nitriles and pentane-2,4-dione react with pentafluorophenylhydrazine through the primary amino-group to afford pyrazoles bearing a preferred 5-amino-over 5-methyl-or 5-hydroxy-substituent in the resulting 4-substituted pyrazoles.