Oxidation of substituted alkyl radicals by hexachloroiridate(2-), hexacyanoferrate(3-), and permanganate ions in aqueous solution. Electron transfer versus chlorine transfer from hexachloroiridate(2-) ion
Palladium catalyzed C<sub>sp2</sub>–H activation for direct aryl hydroxylation: the unprecedented role of 1,4-dioxane as a source of hydroxyl radicals
作者:Kapileswar Seth、Manesh Nautiyal、Priyank Purohit、Naisargee Parikh、Asit K. Chakraborti
DOI:10.1039/c4cc06864e
日期:——
Direct aryl hydroxylation has been achieved via palladium-catalysed Csp2–H activation using versatile directing groups through unprecedented hydroxyl transfer from 1,4-dioxane.
Fragmentation, ring-opening, and addition reactions of oxygen-conjugated alkenyl radicals derived by rapid 1,5-hydrogen shifts in vinyl radicals. An electron spin resonance and kinetic investigation
作者:Bruce C. Gilbert、David J. Parry
DOI:10.1039/p29880000875
日期:——
The addition of ether-derived oxygen-conjugatedradicals ˙CR1R2OCHR1R2 to alkynes R3CCR4 leads to vinylradicals, most of which undergo a rapid 1,5-shift (k > 105 s–1) to give radicals ˙CR1R2OCR1R2CR3CHR4. The reactions of the latter species, as revealed by e.s.r. spectroscopy, include fragmentation (to give R1R2CO and ˙CR1R2CR3CHR4), ring-opening (e.g. for radicals from tetrahydrofuran and dioxane
Methanethiyl radicals (CH3S.) are shown to react with cyclic ethers containing double bonds to give addition and hydrogen abstraction from the allylic positions. The esr spectra of the corresponding radicals have been determined. In some cases radicals arising from a rearrangement (probably 1,4 H-shift) were observed. t-Butoxyl radicals also give abstraction and addition with the same substrates. In
have been determined for the reversible hydrogen-transfer process R˙+ RSH ⇄ RH + RS˙ by pulseradiolysis, mainly through direct observation of the RS˙ radical formation kinetics in water–RH (1 : 1, v/v) mixtures. The thiols investigated were penicillamine and glutathione; the RH hydrogen donors were methanol, ethanol, propan-1-ol, propan-2-ol, ethylene glycol, tetrahydrofuran and 1,4-dioxane with the
已通过脉冲辐解确定了可逆氢转移过程R˙+RSH⇄RH +RS˙的绝对速率常数,主要是通过直接观察水-RH中的RS˙自由基形成动力学来确定的(1:1,v / v)混合物。所研究的硫醇为青霉胺和谷胱甘肽;RH的氢供体为甲醇,乙醇,丙-2-醇,丙-2-醇,乙二醇,四氢呋喃和1,4-二恶烷,其中提取的氢位于羟基或烷氧基官能团的α处。上述平衡的正向反应(在放射生物学中称为“修复”反应)的速率常数通常约为10 7 – 10 8 dm 3 mol –1 s –1而通过硫氢基自由基从RH吸氢(逆过程)的速率常数约为10 3 – 10 4 dm 3 mol –1 s –1。这样产生的平衡常数约为10 4。基于这些数据,标准还原电势可以为R'R来评价“COH / H + // R'R”CHOH,R'R“CO / H + // R'R”C(OH)和R'R“CO //R'R'C˙O -选自甲醇,乙醇和丙-2-醇夫
On the Mechanism of Reaction of Radicals with Tirapazamine
作者:Xiaofeng Shi、Sarah M. Mandel、Matthew S. Platz
DOI:10.1021/ja0647405
日期:2007.4.1
410 nm. The ACOD radical reacts with TPZ in 2-propanol-OD with an absoluterateconstant of (6.7 +/- 0.5) x 108 M-1 s-1, corresponding to a kinetic isotope effect (KIE) of 1.4. Deuteration of the radical on carbon (ACOH-d6) retards the reaction of the radical with TPZ even further (absoluterateconstant = (4.8 +/- 0.04) x 108 M-1 s-1). This result corresponds to a KIE of 2.0. Radicals derived from dioxane