One-pot Preparation of aryl fluorides from anilines under non-aqueous conditions

31 July 2006

Workers at Rhodia have published a one-pot method for fluoro-de-diazonation in organic media. Anilines are converted to the diazonium tetrafluoroborate salt by treatment with boron trifluoride etherate in dichloromethane followed by drop-wise addition of tert-butyl nitrite. If the reaction is carried out at –5ºC, the diazonium salt precipitates out of solution and can be isolated by filtration. But when the reaction is carried out at 20ºC the aryl fluoride is formed directly and can be isolated by standard aqueous quench followed by extraction.

Isolated yields of the tetrafluoroborate salts are in the range 55-80%, whilst the onepot conversions to the fluorides are in the range 25-60%.

* L. Saint-Jalmes et al., Tet. Letts, 2006, 47, 5705-5708.