The photomediated reaction of alkynes with cycloalkanes
作者:Roísín A. Doohan、John J. Hannan、Niall W. A. Geraghty
DOI:10.1039/b517631j
日期:——
of a photomediator such as benzophenone, alkynes with electron-withdrawing groups react with cycloalkanes to give vinyl cycloalkanes. The reaction involves the regiospecific addition of a photochemically generated cycloalkyl radical to the beta-carbon of the alkyne. The stereochemical outcome of the reaction depends on the nature of the photomediator and alkyne used.
Propiolophenone derivatives of the formula ##STR1## wherein R.sup.6 is hydrogen, lower alkyl or a group of the formula ##STR2## as well as corresponding hydroxy compounds of the formula ##STR3## wherein R.sup.6' is hydrogen, lower alkyl, a group of formula (a), (b), (c), (d) or (e) or a group of the formula --C(R.sup.14)(R.sup.15)OR.sup.16' (f'): exhibit mucosa-protective and/or gastric acid secretion-inhibiting properties, such that they can be used for the control or prevention of illnesses of the gastrointestinal tract, especially against gastric ulcers and/or duodenal ulcers.
Catalytic Enantioconvergent Decarboxylative Allylic Alkylation of Allyl Indolenin-3-carboxylates
作者:Thomas M. Kaiser、Jiong Yang
DOI:10.1002/ejoc.201300515
日期:2013.7
A catalytic enantioconvergent process has been developed for the conversion of racemic allyl indolenin-3-carboxylates into enantiomerically enriched C3-quaternary indolenines. A Pd-catalyzeddecarboxylative allylic alkylation reaction was employed for both stereoablation of the racemic allyl indolenin-3-carboxylates and enantioselective formation of the quaternary carbon center.
The unusual geminal hydrogenation of a propargyl alcohol derivative with [CpXRuCl] as the catalyst entails formation of pianostool ruthenium carbenes in the first place; these reactive intermediates can be intercepted with tethered alkenes to give either cyclopropanes or cyclic olefins as the result of a formal metathesis event. The course of the reaction is critically dependent on the substitution
以[Cp X RuCl]为催化剂的炔丙醇衍生物的非常规双氢加氢,首先需要形成钢琴凳形碳烯钌。这些反应性中间体可以通过形式化的复分解事件与链状烯烃截获,生成环丙烷或环状烯烃。反应过程主要取决于烯烃捕集器的取代方式。
Hydrogenative Metathesis of Enynes via Piano-Stool Ruthenium Carbene Complexes Formed by Alkyne <i>gem</i>-Hydrogenation
discovered gem-hydrogenation of internal alkynes is a fundamentally new transformation, in which both H atoms of dihydrogen are transferred to the same C atom of a triple bond while the other position transforms into a discrete metal carbene complex. [Cp*RuCl]4 is presently the catalyst of choice: the resulting piano-stool ruthenium carbenes can engage a tethered alkene into either cyclopropanation or metathesis
最近唯一发现的内部炔烃的宝石氢化是一种全新的转化,其中二氢的两个 H 原子都转移到三键的同一个 C 原子上,而另一个位置转化为离散的金属卡宾配合物。[Cp*RuCl]4 是目前选择的催化剂:所得的钢琴凳式钌卡宾可以与系链烯烃结合进入环丙烷化或复分解,并且这种反应性中间体的典型例子与连接到钌中心的烯烃通过 X 射线衍射分离和表征。烯烃的取代模式决定了是否发生复分解或环丙烷化:使用性质大不相同的烯烃进行系统调查,并结合局部耦合簇理论水平的机理计算研究,可以对制备结果进行分类,并提出具有预测能力的直观模型。如果发生复分解,该模型将反应过程与双键的极化以及形成的二级卡宾配合物的稳定性联系起来。“氢化复分解”首次应用于 sinularones E 和 F 的全合成与这种解释一致,并允许这些海洋天然产物的拟议结构得到证实。在此合成过程中,发现宝石氢化也为 C-H 功能化提供了机会。而且,甲硅烷基化炔烃