Bis-triethylene Glycolic Crown-5-calix[4]arene: A Promoter of Nucleophilic Fluorination Using Potassium Fluoride.

We designed and synthesized a bis-triethylene glycolic crown-5-calix[4]arene (BTC5A) as a multifunctional promoter for nucleophilic fluorination using KF. The synergetic effect of the calix-crown moiety and ethylene glycols of BTC5A enabled KF to be easily dissolved in organic solvents and activated the fluoride in even nonpolar aprotic media. To validate its practicality, the SN2 fluorinations including 18F-fluorination of various substrates were successfully conducted using KF(or [18F]F-) in the presence of BTC5A.