描述了使用基于钌的复分解催化剂的 Z 选择性大环化的第一份报告。对于具有各种官能团和环大小的多种底物,Z 大环的选择性始终很高。同样的催化剂也用于 E 和 Z 大环混合物的 Z 选择性乙烯醇解,提供纯 E 异构体。值得注意的是,只需要 1 个大气压的乙烯压力。这些方法已成功应用于几种嗅觉大环化合物的构建以及细胞毒性生物碱莫托泊明 C 的正式全合成。
The synthesis of macrocycles is severely impeded by concomitant oligomer formation. Here, we present a biomimetic approach that utilizes spatial confinement to increase macrocyclization selectivity in the ring clos-ing metathesis of various dienes at elevated substrate concentration up to 25 mM using an olefin me-tathesis catalyst selectively immobilized inside ordered mesoporous silicas with defined
Polymer Skeletal Editing via Anionic Brook Rearrangements
作者:Maxim Ratushnyy、Aleksandr V. Zhukhovitskiy
DOI:10.1021/jacs.1c06860
日期:2021.11.3
communicates the first example of polymerbackbone metamorphosis affected by anionic 1,2-Brook rearrangement of acyl silane moieties. Introduction of the acyl silane functionality into a polymerbackbone was achieved via acyclic diene metathesis copolymerization (ADMET) of diene 1 and two dienes. We demonstrate that, using organolithium species and cyanide as nucleophiles, the backbones of resulting copolymers
Macrocyclization of Dienes under Confinement with Cationic Tungsten Imido/Oxo Alkylidene <i>N</i>‐Heterocyclic Carbene Complexes
作者:Felix Ziegler、Johanna R. Bruckner、Michal Nowakowski、Matthias Bauer、Patrick Probst、Boshra Atwi、Michael R. Buchmeiser
DOI:10.1002/cctc.202300871
日期:2023.11.8
Two tungsten-based catalysts have been selectively immobilized within the pores of ordered mesoporous silica materials. X-ray absorption spectroscopy confirm the structural integrity of the catalysts. Compared to the homogenous analogues, the immobilized tungsten-catalysts exhibit a substantially increased macrocyclization- and Z-selectivity, which allow for the use of high substrate concentrations
Oligomers as Intermediates in Ring-Closing Metathesis
作者:Jay C. Conrad、Melanie D. Eelman、João A. Duarte Silva、Sebastien Monfette、Henrietta H. Parnas、Jennifer L. Snelgrove、Deryn E. Fogg
DOI:10.1021/ja067531t
日期:2007.2.1
Oligomerization is kinetically favored in RCM reactions catalyzed by RuCl2(PCy3)(IMes)(=CHPh), for a range of unhindered , alpha,omega-dienes leading to large or medium-sized rings, even at dilutions designed to minimize intermolecular reaction. Reversible metathesis (i.e., ethenolysis) is inhibited by rapid volatilization of ethylene. At appropriately high dilutions, however, the RCM products are efficiently liberated by backbiting.
Highly Selective Macrocycle Formations by Metathesis Catalysts Fixated in Nanopores
作者:Joo-Eun Jee、Jian Liang Cheong、Jaehong Lim、Cheng Chen、Soon Hyeok Hong、Su Seong Lee
DOI:10.1021/jo302823w
日期:2013.4.5
Ruthenium-based metathesis catalysts immobilized on mesocellular siliceous foam (MCF) bearing large nanopores proved highly efficient and selective for macrocyclic ring-closing metathesis (RCM). Kinetic studies revealed that the homogeneous counterpart exhibited far higher activity that accounted for more oligomerization pathways and resulted in less macrocyclization products. Meanwhile, the immobilized catalysts showed lower conversion rates leading to higher yields of macrocyclic products in a given reaction time, with conversion rates and yields dependent upon pore size, catalyst loading density, and linker length. The macrocycle formations via RCM were accelerated by increasing the pore size and decreasing the catalyst loading density while retaining the comparably high yield. The catalysts immobilized on MCF, of which silica surface is rigid and pores are relatively large, showed high conversion rates and yields compared with an analogue immobilized on TentaGel resins, of which backbone becomes flexible upon swelling in the reaction medium. It is noteworthy that the selectivity for the macrocyclic RCM can be significantly improved by tuning the catalyst initiation rates via immobilization onto the support materials in which well-defined three-dimentional network of large nanopores are deployed.