The Smiles Rearrangement of Fluorinated Hydrazonoyl Esters to Unsymmetrical N',N'-Diaryl Acylhydrazines.

Two-step telescopic synthesis of unsymmetrical diarylhydrazides formally derived from di- and trifluoroacetic acid is reported. The method comprises trapping of the in situ-generated 1,3-dipolar di- and trifluoroacetonitrile imine with phenolate, followed by the Smiles rearrangement of the initially formed hydrazonoyl ester. Mechanistic analysis of the second step using DFT calculations revealed a single-step aryl migration proceeding through a pseudocyclic transition state and exhibiting only a minor influence of the fluoromethyl substituent. The structures of selected CF3- and CHF2-functionalized products were confirmed by X-ray analysis.