Reactions of dibromotetrafluorobenzene derivatives with sodium phenoxide salts. Competing hydrodebromination and SNAr processes

1,2- and 1,3-dibromotetrafluorobenzene react with sodium phenoxide derivatives at sites para to ring bromine because these positions are activated by fluorine atoms ortho and meta to the site of nucleophilic substitution. Fluorine para to the site of nucleophilic attack is usually deactivating in nucleophilic aromatic substitution processes and this is reflected in the significantly reduced reactivity of 1,4-dibromotetrafluorobenzene which undergoes competing hydrodebromination processes to afford, primarily, 3-bromo-1,2,4,5-tetrafluorobenzene.

Graphical abstractReactions of sodium phenoxide with dibromotetrafluorobenzene derivatives give products arising from substitution of the fluorine atom or hydrodebromination depending on the substrate.Figure optionsDownload full-size imageDownload as PowerPoint slide