2-, 3- and 4-[<sup>18</sup>F]Fluoropyridine by no-carrier-added nucleophilic aromatic substitution with K[<sup>18</sup>F]F-K<sub>222</sub>- a comparative study
作者:M. Karramkam、F. Hinnen、F. Vaufrey、F. Dollé
DOI:10.1002/jlcr.730
日期:2003.9
Compared to homoaromatic and aliphatic nucleophilic radiofluorinations, only few references can be found in the literature describing nucleophilic substitutions with [18F]fluoride ion of heteroaromatic compounds such as pyridines and only reactions involving fluorination processes at the ortho-position (2-position) have been more intensively studied. In the present paper, the scope of the nucleophilic aromatic fluorinations at the meta- and para-position of the pyridine ring with no-carrier-added [18F]fluoride ion as its activated K[18F]F-K222 complex has been evaluated and compared to the nucleophilic aromatic fluorinations at the ortho-position in this pyridine series. The syntheses of 3- and 4-[18F]fluoropyridines were chosen as model reactions and compared to the radiosynthesis of 2-[18F]fluoropyridine. The parameters studied include the influence of the position of the leaving group at the pyridine ring, as well as the quantity of the precursor used, the type of activation (conventional heating, microwave irradiation), the solvent, the temperature and the reaction time. Using the corresponding nitro precursor, high yields were obtained at the 2-position (94% yield) using microwaves (100 W) for 2 min in DMSO. Good yields (up to 72%) were observed at the 4-position using the same conditions while practically no reaction was observed at the 3-position. About 60% yield was also obtained at both the 2- and 4-position using the corresponding nitro precursor at 145°C for 10 min in DMSO. Copyright © 2003 John Wiley & Sons, Ltd.
与富电子芳香型和脂肪型亲核氟化反应相比,文献中关于吡啶等杂芳香化合物与[18 F]氟离子进行亲核取代反应的报道很少,且仅对邻位(2位)氟化反应进行了较深入的研究。本文评估了无载体[18 F]氟离子以活化K[18 F]F-K222复合物形式在吡啶环间位和对位进行的亲核芳香氟化反应范围,并与该吡啶系列中邻位亲核芳香氟化反应进行了比较。以3-和4-[18 F]氟吡啶的合成作为模型反应,并与2-[18 F]氟吡啶的放射合成进行了比较。研究了吡啶环上离去基团的位置、前体用量、活化类型(常规加热、微波辐照)、溶剂、温度和反应时间等因素的影响。使用相应的硝基前体,在二甲基亚砜中用微波(100 W)辐照2分钟,获得了高产率(94%)。在4位使用相同条件获得了良好产率(最高72%),而在3位几乎没有反应。在二甲基亚砜中145°C下使用相应的硝基前体10分钟,在2位和4位均获得了约60%的产率。Copyright © 2003 John Wiley & Sons, Ltd.