Substitution-reduction: an alternative process for the[18F]N-(2-fluoroethylation) of anilines
作者:Emmanuelle Briard、Victor W. Pike
DOI:10.1002/jlcr.816
日期:2004.3.30
Substitution of a halo atom (chloro or bromo) in easily prepared N-haloacetyl-anilines with no-carrier added (NCA) cyclotron-produced [18F]fluoride ion (18F, t1/2= 109.8 min; β+=96.9%), followed by reduction with borane–tetrahydrofuran (BH3–THF), provides an alternative route to NCA [18F]N-(2-fluoroethyl)-anilines. This two-step and one-pot process is rapid (∼50 min) and moderately high yielding (∼40% decay-corrected radiochemical yield (RCY) overall). In the nucleophilic substitution reaction, 18-crown-6 is preferred to Kryptofix® 222 as complexing agent for the solubilization of the counter-ion (K+), derived from an added metal salt, in acetonitrile. Weakly basic potassium bicarbonate is preferred as the added metal salt. Inclusion of a small amount of water, equating to 4–5 molar equivalents relative to 18-crown-6, base or precursor (held in equimolar ratio), is beneficial in preventing the adsorption of radioactivity onto the wall of the glass reaction vessel and for achieving high RCY in the nucleophilic substitution reaction. BH3–THF is effective for the rapid reduction of the generated [18F]N-fluoroacetyl-aniline to the [18F]N-(2-fluoroethyl)-aniline. Copyright © 2004 John Wiley & Sons, Ltd.
用无载体添加(NCA)回旋加速器产生的[18F]氟离子(18F,t1/2= 109.8 分钟;β+=96.9%)取代容易制备的 N-卤乙酰基苯胺中的卤原子(氯或溴),然后用硼烷-四氢呋喃(BH3-THF)还原,为 NCA [18F]N-(2-fluoroethyl)-anilines 提供了另一条途径。这种两步一锅的工艺快速(∼50 分钟),产率适中(总体衰变校正放射化学产率(RCY)∼40%)。在亲核取代反应中,18-crown-6 比 Kryptofix® 222 更适合作为络合剂,用于在乙腈中溶解由添加的金属盐产生的反离子(K+)。添加的金属盐以弱碱性碳酸氢钾为佳。加入少量水(相当于 18-冠醚-6、碱或前体(以等摩尔比保持)的 4-5 摩尔当量)有利于防止放射性吸附到玻璃反应容器壁上,并在亲核取代反应中获得高 RCY。BH3-THF 能有效地将生成的[18F]N-氟乙酰基苯胺快速还原为[18F]N-(2-氟乙基)苯胺。Copyright © 2004 John Wiley & Sons, Ltd. All Rights Reserved.