Aromatic radical anions as possible intermediates in the nucleophilic aromatic substitution (SNAr): an EPR study
作者:Loris Grossi、Samantha Strazzari
DOI:10.1039/a903407b
日期:——
The reactions among halonitrobenzenes or polynitrobenzenes and alkoxides, thiolates or tertiary amines have provided the evidence that in a SNAr reaction type a single electron transfer from the nucleophile to the aromatic substrate, to generate two radical species within the solvent cage, can take place to some extent. The detection of radical intermediates by EPR spectroscopy, in several SNAr reactions
卤代硝基苯或多硝基苯与醇盐,硫醇盐或叔胺之间的反应提供了证据,表明在S N Ar反应类型中,可以发生从亲核体到芳族底物的单电子转移,从而在溶剂笼内产生两个自由基在某种程度上。通过EPR光谱学,在几μs自由基中间体的检测Ñ氩反应报道。
Base-catalyzed autoxidation of trialkylamines. An e.s.r study
作者:Loris Grossi
DOI:10.1016/s0040-4039(00)95520-5
日期:1987.1
When a freshly distilled tertiary alkyl amine is dissolved in water a base-catalyzed oxidative dealkylation process takes place, leading to the formation of secondary nitroxyl radicals, alkenes and carbonyl-containing compounds.
The radical-initiated reaction of tris(trimethylsilyl)silane with a variety of aliphatic nitro derivatives has been investigated. This silane, which for many applications is a valid alternative to tributyltin hydride, is unable to reduce tertiary nitroalkanes to the corresponding hydrocarbons. EPR results, as well as kinetic and products studies, have shown that this ''anomalous'' behavior is due to the fact that the nitroxide adducts formed by addition of tris(trimethylsilyl)silyl radicals to the nitro compounds fragment preferentially at the nitrogen-oxygen bond rather than at the carbon-nitrogen bond as in the analogous tributyltin adducts. The resulting silyloxy radical, (Me3Si)3SiO+, undergoes a fast rearrangement (k greater-than-or-equal-to 10(7) s-1 at room temperature) with migration of a Me3Si group from silicon to oxygen to give (Me3Si)2SiOSiMe3 which adds to the nitro compound affording a secondary nitroxide adduct. The kinetics of the decay of both primary and secondary adducts to nitromethane has been studied over a wide range of temperatures. With tertiary nitroalkanes persistent aminyl radicals, RNOSi(SiMe3)3, have also been detected.