TY - JOUR

T1 - Homogeneous Nucleophilic Radiofluorination and Fluorination with Phosphazene Hydrofluorides

A1 - Mathiessen,Bente

A1 - Jensen,Andreas Tue Ingemann

A1 - Zhuravlev,Fedor

AU - Mathiessen,Bente

AU - Jensen,Andreas Tue Ingemann

AU - Zhuravlev,Fedor

PB - Wiley - V C H Verlag GmbH & Co. KGaA

PY - 2011

Y1 - 2011

N2 - A series of phosphazenium hydrofluorides, P1tBu⋅[18/19F]HF, P1tOct⋅[18/19F]HF, P2Et⋅[18/19F]HF, and P4tBu⋅[18/19F]HF, was synthesized. The radioactive phosphazenium [18F]hydrofluorides were obtained by the one‐step formation and trapping of gaseous [18F]HF with the respective phosphazene bases. The [19F] isotopomers were prepared from the corresponding phosphazene bases and Et3N⋅3HF. Under the design of experiment (DoE)‐optimized conditions, P2Et⋅HF and P4tBu⋅HF fluorinated alkyl chlorides, bromides, and pseudohalides in 76–98 % yield, but gave lower yields with iodides and electron‐deficient arenes. DoE models showed that fluorination can be performed in glass vessels, and that the reactivity of P2Et⋅HF and P4tBu⋅HF is dominated by solvent polarity but is insensitive to water to at least 2 equiv. In contrast, P1tBu⋅HF and P1tOct⋅HF were unstable towards autofluorolysis. DFT calculations were performed to rationalize this finding in terms of diminished steric bulk, higher Parr’s electrophilicity, and chemical hardness of P1RH+. The corresponding radiofluorination reaction gave no valid DoE model but displayed similar substrate scope. High specific activity and excellent radiochemical yields with various pseudohalides (81–91 %) suggest that the proposed radiofluorination methodology can complement the current [18F]KF/Kryptofix methods, particularly in the areas for which nonpolar reaction conditions are required.

AB - A series of phosphazenium hydrofluorides, P1tBu⋅[18/19F]HF, P1tOct⋅[18/19F]HF, P2Et⋅[18/19F]HF, and P4tBu⋅[18/19F]HF, was synthesized. The radioactive phosphazenium [18F]hydrofluorides were obtained by the one‐step formation and trapping of gaseous [18F]HF with the respective phosphazene bases. The [19F] isotopomers were prepared from the corresponding phosphazene bases and Et3N⋅3HF. Under the design of experiment (DoE)‐optimized conditions, P2Et⋅HF and P4tBu⋅HF fluorinated alkyl chlorides, bromides, and pseudohalides in 76–98 % yield, but gave lower yields with iodides and electron‐deficient arenes. DoE models showed that fluorination can be performed in glass vessels, and that the reactivity of P2Et⋅HF and P4tBu⋅HF is dominated by solvent polarity but is insensitive to water to at least 2 equiv. In contrast, P1tBu⋅HF and P1tOct⋅HF were unstable towards autofluorolysis. DFT calculations were performed to rationalize this finding in terms of diminished steric bulk, higher Parr’s electrophilicity, and chemical hardness of P1RH+. The corresponding radiofluorination reaction gave no valid DoE model but displayed similar substrate scope. High specific activity and excellent radiochemical yields with various pseudohalides (81–91 %) suggest that the proposed radiofluorination methodology can complement the current [18F]KF/Kryptofix methods, particularly in the areas for which nonpolar reaction conditions are required.

KW - Hevesy laboratory

KW - Hevesy laboratoriet

U2 - 10.1002/chem.201100458

DO - 10.1002/chem.201100458

JO - Chemistry: A European Journal

JF - Chemistry: A European Journal

SN - 0947-6539

IS - 28

VL - 17

SP - 7796

EP - 7805

ER -