Z-Selective Ring-Closing Metathesis Catalysts
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Solution Overview
Problem
Catalytic ring-closing metathesis (RCM) reactions lack control over alkene stereoselectivity, particularly for larger rings, leading to inefficient synthesis of Z macrocyclic alkenes, which are crucial for biologically active molecules like epothilone and nakadomarin A, due to the reversibility of olefin metathesis and preference for lower energy E isomers.
Innovation Solution
The use of molybdenum- or tungsten-based catalysts in Z-selective ring-closing metathesis reactions, which promote the formation of Z macrocyclic alkenes with high stereoselectivity, even at higher concentrations, by minimizing undesired E isomerization and homocoupling, and allowing for efficient synthesis of biologically active compounds like epothilone A and nakadomarin A.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional catalytic ring-closing metathesis is used for macrocyclic synthesis, then the reaction proceeds with high efficiency, but the alkene stereoselectivity is minimal and the E isomer is strongly preferred
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by using molybdenum or tungsten-based catalysts with specific ligand environments instead of traditional ruthenium catalysts. This parameter change in catalyst identity and structure enables Z-selective macrocyclic RCM reactions, achieving up to 97% Z-stereoselectivity while maintaining high reaction efficiency and productivity.
2Manufacturing precision
If thermodynamic control is used for larger ring structures, then the reaction proceeds smoothly, but the energy difference between E and Z isomers is insufficient to achieve high stereoselectivity
Solution Approach 1:
The patent applies preliminary action by designing catalysts with specific ligand environments (such as N-heterocyclic carbenes or phosphine ligands) that create a sterically and electronically controlled environment before the reaction occurs. This preliminary catalyst design establishes kinetic control over the reaction pathway, favoring Z-isomer formation through transition state stabilization, thereby achieving high stereoselectivity independent of the thermodynamic stability difference between E and Z isomers.
3Productivity
If the reaction proceeds to completion, then the yield increases, but the higher energy Z isomer is converted to the lower energy E form through post-RCM isomerization
Solution Approach 1:
The patent converts the potential harm of isomerization into a benefit by using molybdenum or tungsten catalysts that exhibit unique dual functionality: they catalyze both the RCM reaction and the isomerization, but in a controlled manner. The catalyst system is designed to favor Z-isomer formation kinetically while suppressing E-isomer formation, effectively using the catalyst's ability to promote isomerization to maintain Z-selectivity throughout the reaction, thereby achieving both high yield and high stereoisomeric purity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves up to 97% Z-selectivity in macrocyclic alkene formation, overcoming the limitations of traditional RCM methods by providing a reliable and efficient route to Z macrocyclic alkenes, enhancing the synthesis of complex natural products with improved stereoselectivity and yield.
Implementation Method 1
The use of molybdenum- or tungsten-based catalysts in Z-selective ring-closing metathesis reactions, which promote the formation of Z macrocyclic alkenes with high stereoselectivity
Implementation Method 2
Catalytic ring-closing metathesis (RCM) is an indispensable method for the preparation of cyclic structures of various sizes
Data Source
AI summary
The present invention relates generally to olefin metathesis. In some embodiments, the present invention provides methods for Z-selective ring-closing metathesis.