The oxidative conversion of silylenolethers to α,β-unsaturated ketones using a less-hindered class of oxoammonium salts (AZADO+BF4–) is described. The reaction proceeds via the ene-like addition of oxoammonium salts to silylenolethers.
effects of ethylene glycol-derived alcohols/hemiacetals on inhibiting oxidation catalysts. Herein, using a CuCl/tetramethylethylenediamine/1,5-dimethyl-9-azanoradamantane N-oxyl catalyst, we describe a highlyefficient aerobic oxidative esterification reaction of ethylene glycol to various oxalic acid diesters via selective oxidation of ethylene glycol-derived alcohols/hemiacetals even in the presence
理想的绿色酯化反应之一是需氧氧化酯化反应,该反应仅使用化学计量的不同醇,通过分子间选择性醇氧化,然后通过将其他醇和半缩醛氧化加入酯形成半缩醛。然而,迄今为止尚未报道通过氧化酯化合成草酸二酯,这可能是由于分子间醇氧化的选择性控制困难以及乙二醇衍生的醇/半缩醛对抑制氧化催化剂的螯合作用。在此,使用 CuCl/四甲基乙二胺/1,5-二甲基-9-氮杂金刚烷N-oxyl 催化剂,我们描述了即使在其他脂肪族伯醇存在下,通过乙二醇衍生的醇/半缩醛的选择性氧化,乙二醇对各种草酸二酯的高效好氧氧化酯化反应。值得注意的是,使用乙二醇和伯/仲醇的理想化学计量比,绿色反应效果很好。彻底的实验研究和理论计算表明,高选择性的氧化酯化是通过乙二醇衍生的醇/半缩醛与 Cu( II ) 物种的优先双齿配位实现的,然后是有效的双电子/单质子转移。
Persistent four-coordinate iron-centered radical stabilized by π-donation
Chemical modifications' of native proteins can facilitate production of supernatural protein :functions that are not easily accessible by complementary methods relying on genetic manipulations. However, accomplishing precise control over selectivity while maintaining structural:. integrity and homogeneity still represents a fOrmidable, challenge. Herein, we report a transition metal-free method for tryptophan-selective bioconjugation of proteins that is based on an organoradical and operates under ambient conditions. This method exhibits low levels of cross-reactivity and leaves.higher-order structures of the protein and various functional groups therein unaffected: The strategy to,target less abundant amino acids contributes to the formation of structurally homogeneous conjugates, which may even be suitable for protein. crystallography. The absence of toxic metals and biochemi-i cally incompatible conditions allows a rapid functional- modulation of native proteins such as antibodies and pathogenic aggregative proteins, and this method may thus easily find therapeutic applications.