Difluoroacetates are versatile precursors for the synthesis of difluoromethyl compounds or for the introduction of ¹⁸F labels. Thus, they have applications in drug discovery and total synthesis.

Sripati Jana and Rene M. Koenigs, RWTH Aachen University, Germany, have developed a protocol that allows the introduction of a difluoroacetate-thioether into diazoesters (product pictured). The team used a readily available Rh^II catalyst, Rh₂(OAc)₄, to promote a reaction between a diazoacetate and an allylic sulfide bearing a difluoroacetate substituent.

The diazoacetate acts as a carbene source. The carbene then undergoes an addition reaction with the sulfide compound and forms an ylide intermediate. This ylide undergoes a [2,3]‐sigmatropic rearrangement to give the product. This type of reaction is called a Doyle–Kirmse rearrangement.

The desired fluorinated homoallylic sulfides were obtained in good to excellent yields (up to 91 %). The reaction can also be performed under metal‐free conditions if visible light is used to generate the carbene intermediate.

• Doyle–Kirmse Rearrangement Reactions of Difluoroacetates,
  Sripati Jana, Rene M. Koenigs,
  Asian J. Org. Chem. 2019.
  https://doi.org/10.1002/ajoc.201900099