作者:Lennart Eberson、Ola Persson
DOI:10.1039/a607509f
日期:——
The reactions of two fluorinating reagents, XeF2 and
N-fluorodibenzenesulfonamide
[(PhSO2)2N–F], with several spin traps have
been investigated. In dichloromethane, the strong oxidant
XeF2 cleanly gives fluoro spin adducts with
N-tert-butyl-α-phenylnitrone
(PBN) or 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) according to a
mechanism mediated by the radical cation of the spin trap. In both
cases, further fluorination takes place with replacement of the α
hydrogen by fluorine.The much weaker oxidant (PhSO2)2N–F
reacts with PBN or DMPO in dichloromethane giving both the fluoro adduct
and an adduct formally derived from an N-centred
radical, assigned the structure of
PhSO2N(F)–PBN˙ or
(PhSO2)2N–DMPO˙, respectively. This
type of reaction proceeds by a version of the Forrester–Hepburn
mechanism, in which an acid HA, in this case HF, initially adds to the
nitrone function to give a hydroxylamine derivative which is oxidized by
(PhSO2)N–F giving the fluoro spin adduct, a proton and
the highly labile radical anion
(PhSO2)2N–F˙-
. By
decomposition of the latter to PhSO2(F)N-
and PhSO2˙, conditions are set up for propagation of
the reaction by a new molecule of HA [now PhSO2(F)NH] and
thus formation of the PhSO2(F)N spin adduct.
两种氟化剂XeF2和XeF2的反应
N-氟二苯磺酰胺
[(PhSO2)2N–F],与几个自旋陷阱有
被调查。二氯甲烷中的强氧化剂
XeF2 干净地产生氟自旋加合物
N-叔丁基-α-苯基硝酮
(PBN) 或 5,5-二甲基-1-吡咯啉 1-氧化物 (DMPO) 根据
由自旋陷阱的自由基阳离子介导的机制。在两者中
在这种情况下,通过取代α进行进一步氟化
氟与氢反应。弱得多的氧化剂 (PhSO2)2N–F
在二氯甲烷中与 PBN 或 DMPO 反应,生成氟加合物
以及形式上源自 N 中心的加合物
根式,指定结构
PhSO2N(F)–PBN˙ 或
分别为(PhSO2)2N–DMPO˙。这
福雷斯特-赫本反应的一个版本进行的反应类型
机制,其中酸性 HA(在本例中为 HF)最初添加到
硝酮功能产生羟胺衍生物,该衍生物被氧化
(PhSO2)N–F 产生氟自旋加合物、质子和
高度不稳定的自由基阴离子
(PhSO2)2N–F˙-
。经过
后者分解为PhSO2(F)N-
和PhSO2˙,为传播设置了条件
新的 HA 分子 [现为 PhSO2(F)NH] 的反应
从而形成PhSO2(F)N自旋加合物。