prepared and tested as simple catalysts of oxidations with hydrogen peroxide, using sulfoxidation as a model reaction. Their catalyticefficiency strongly depends on the type of substituent and is remarkable for derivatives with an electron-withdrawing group, showing reactivity comparable to that of flaviniumsalts which are the prominent organocatalysts for oxygenations. Because of their high stability
制备了一系列的单取代的嘧啶鎓和吡嗪鎓三氟甲磺酸酯和3,5-二取代的吡啶鎓三氟甲磺酸酯,并使用硫氧化作为模型反应,对过氧化氢的简单氧化催化剂进行了测试。它们的催化效率在很大程度上取决于取代基的类型,并且对于具有吸电子基团的衍生物而言是显着的,其反应性与黄酮盐相当,后者是氧合作用的主要有机催化剂。由于它们的高稳定性和良好的可及性,4-(三氟甲基)嘧啶鎓和3,5-二硝基吡啶鎓三氟甲磺酸盐是选择的催化剂,并显示出催化脂肪族和芳香族硫化物氧化为亚砜的作用,定量转化率高,制备产率高,并且具有优异的性能。化学选择性。K R +值(p K R + <5)和较小的负还原电位(E red > -0.5 V)。在催化氧化过程中原位形成的过氧化氢加合物充当底物氧化剂。通过在B3LYP / 6-311 ++ g(d,p)水平上的计算获得的从这些杂环氢过氧化物到硫代苯甲醚的转移的吉布斯自由能表明,它们是比烷基氢过氧化
Two-Phase Oxidations with Aqueous Hydrogen Peroxide Catalyzed by Amphiphilic Pyridinium and Diazinium Salts
作者:Tomáš Hartman、Jiří Šturala、Radek Cibulka
DOI:10.1002/adsc.201500687
日期:2015.11.16
Amphiphilic pyridinium and diazinium salts were shown to be effective catalysts in two-phase (water/chloroform or water/dichloromethane) sulfoxidations and N-oxidations with hydrogenperoxide under mild conditions. This unprecedented oxidation method utilizes covalent bonding of hydrogenperoxide to a simple pyridinium or diazinium nucleus to increase the lipophilicity of the hydroperoxide species
The synthesis of nebularine and its analogs <i>via</i> oxidative desulfuration in aqueous nitric acid
作者:Ran Xia、Li-Ping Sun、Gui-Rong Qu
DOI:10.1080/10426507.2016.1225057
日期:2017.1.2
GRAPHICAL ABSTRACT ABSTRACT The synthesis of nebularine and its analogs has been achieved via oxidative desulfuration in H2O for the first time. With 50% HNO3 as an oxidant and solvent, 18 products were obtained in good yields (70%–94%). The oxidative desulfuration system could tolerate different functional groups including fluoro, chloro, amino, alkyl, allyl, ribosyl, deoxyribosyl, and arabinofuranosyl
Substituent Effects on Photochemical Hydrogen Abstraction in 2-Acylpyridines, 2-Acylpyrazines, and 4-Acylpyrimidines
作者:C. Janakiram Rao、William C. Agosta
DOI:10.1021/jo00087a032
日期:1994.4
Stern-Volmer quenching of the photochemistry of 1c indicates that N- and O-abstraction (eqs 1 and 2, respectively) are quenched at different rates (Figure 1). For quenching of 2c k(q) tau is 157 M(-1) and for 3c, 64 M(-1). When 1c is sensitized with triplet sensitizers of increasing E(T), N-abstraction increases (Table 1). These data indicate that N- and O-abstraction in 1c take place from distinguishable triplet states. Survey of Phi(p)'s of ring-substituted ketones 1b-d, 6d, 7a,b,d, 8b, 9b,d, 10b, and 11d demonstrates the effect of substitution on the competition between N- and O-abstraction (Table 2). For methyl- and diacyano-substituted ketones, the results can be understood simply in terms of shifts in E(T) of the n pi* and pi pi* states of the heterocycle. The photochemistry of all these ketones requires consideration of interactions among three triplet states.
4-Trifluoromethylpyrimidines
作者:I. I. Gerus、S. I. Vdovenko、M. G. Gorbunova、V. P. Kukhar'