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
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。
Regiochemistry and stereochemistry of intramolecular [2+2] photocycloaddition of carbon-carbon double bonds to cyclohexenones
作者:D. Becker、M. Nagler、Y. Sahali、N. Haddad
DOI:10.1021/jo00014a040
日期:1991.7
The intramolecular [2 + 2] photocycloaddition mechanism of alkenes tethered by a three-methylene chain to cyclohexenones has been studied. It was found that the reversion from a 1,4-diradical intermediate to starting material is slow relative to the rate of photoadduct formation. Only ''straight'' closure was observed in the systems studied. For compounds 1-3 and 5, the assumption that the first bond is formed between the beta-carbon of the enone and C-4' leading to a 1,4-diradical is supported. For the formation of compounds 6-11, possible mechanisms are discussed.