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
Asymmetric Reductive and Alkynylative Heck Bicyclization of Enynes to Access Conformationally Restricted Aza[3.1.0]bicycles
作者:Xiaolei Huang、Minh Hieu Nguyen、Maoping Pu、Luoqiang Zhang、Yonggui Robin Chi、Yun‐Dong Wu、Jianrong Steve Zhou
DOI:10.1002/anie.202000859
日期:2020.6.26
Conformationallyrestricted azabicycles are becoming increasingly important in medicinal research. Asymmetric Heck bicyclization of enynes proceeds to give medicinally useful aza[3.1.0] and aza[4.1.0] bicycles with excellent enantioselectivity. The key organopalladium species after bicyclization can be trapped by silanes and terminal alkynes.
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。
Practical Cobalt Carbonyl Catalysis in the Thermal Pauson−Khand Reaction: Efficiency Enhancement Using Lewis Bases
作者:Marie E. Krafft、Llorente V. R. Boñaga、Chitaru Hirosawa
DOI:10.1021/jo0057708
日期:2001.5.1
In this report we have shown that the commercially available Co-2(CO)(8) and CO4(CO)(12), and enyne-Co-2(CO)(6) complexes, are sufficiently effective in catalyzing the Pauson-Khand reaction under one atmosphere of CO pressure. It was further demonstrated that the efficiencies of these cyclization protocols could be enhanced by the presence of cyclohexylamine. These procedures have also rendered more practical and highly convenient alternatives for the catalytic Pauson-Khand reaction. Most importantly, we have dispelled the common belief that Co-4(CO)(12) is inactive in the Pauson-Khand reaction under one atmosphere of carbon monoxide. Of mechanistic importance is that these studies have also shown that the probable formation of Co-4(Co)(12) is not necessarily a dead end pathway in the Co-2(CO)(8)-catalyzed Pauson-Khand reaction. It is also of interest that substoiciometric amounts of Co-2(CO)(8), in DME and in the presence of cyclohexylamine, are sufficient for the cyclocarbonylation of enynes under a nitrogen atmosphere. Our findings have provided more practical protocols for the Pauson-Khand reaction using catalytic amounts of cobalt carbonyl complexes and a better understanding of the influence of Lewis bases on their efficiency. These reports on the activity of CO4(CO)(12) are anticipated to develop into a convenient and practical alternative for Co-2(CO)(8) catalysis.
Krafft, Marie E.; Boñaga, Llorente V. R., Synlett, 2000, # 7, p. 959 - 962