In:
Chemistry – A European Journal, Wiley, Vol. 17, No. 28 ( 2011-07-04), p. 7796-7805
Abstract:
A series of phosphazenium hydrofluorides, P 1 t Bu ⋅ [ 18/19 F]HF, P 1 t Oct ⋅ [ 18/19 F]HF, P 2 Et ⋅ [ 18/19 F]HF, and P 4 t Bu ⋅ [ 18/19 F]HF, was synthesized. The radioactive phosphazenium [ 18 F]hydrofluorides were obtained by the one‐step formation and trapping of gaseous [ 18 F]HF with the respective phosphazene bases. The [ 19 F] isotopomers were prepared from the corresponding phosphazene bases and Et 3 N ⋅ 3HF. Under the design of experiment (DoE)‐optimized conditions, P 2 Et ⋅ HF and P 4 t Bu ⋅ 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 P 2 Et ⋅ HF and P 4 t Bu ⋅ HF is dominated by solvent polarity but is insensitive to water to at least 2 equiv. In contrast, P 1 t Bu ⋅ HF and P 1 t Oct ⋅ 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 P 1 R H + . 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 [ 18 F]KF/Kryptofix methods, particularly in the areas for which nonpolar reaction conditions are required.
Type of Medium:
Online Resource
ISSN:
0947-6539
,
1521-3765
DOI:
10.1002/chem.201100458
Language:
English
Publisher:
Wiley
Publication Date:
2011
detail.hit.zdb_id:
1478547-X
Permalink