Catalytic and asymmetric fluorolactonisations of carboxylic acids through anion phase transfer

Catalytic fluorolactonisations of aromatic carboxylic acids have been developed. The reactions proceed under mild conditions using the commercially available reagent Selectfluor. A weak phase transfer of the reagent mediated by Na₂CO₃ allows the reaction to be conducted in non-polar solvents. Furthermore, by the use of a catalytic amount of (DHQ)₂PHAL (hydroquinine 1,4-phthalazinediyl diether), the first asymmetric fluorolactonisation has been achieved. The corresponding isobenzofuran core can be found in many biologically active molecules. Don't fluoro-get me! An almost forgotten mode of halolactonisation, namely the fluorolactonisation has been developed with aryl carboxylic acids to give fluorinated isobenzofurans (see scheme). This mild and simple procedure can be conducted in non-polar solvents. In addition the first example of an asymmetric variant is also presented.