Z-Selective Olefin Metathesis Catalyst Ligand Design
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Solution Overview
Problem
Current methods for metathesis reactions produce mixtures of Z- and E-isomers, making it difficult to achieve high selectivity for the Z-isomer of internal olefins, which are crucial for pharmaceutical and natural product synthesis, due to the lack of efficient catalysts that can selectively form Z-isomers.
Innovation Solution
Development of catalysts with specific structures, such as those containing Mo or W with oxygen and nitrogen-containing ligands, that facilitate high Z-selectivity in homo-metathesis reactions of terminal olefins, allowing for the production of internal double bonds with a high percentage of Z-isomer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional metathesis catalysts are used, then metathesis reaction can proceed, but a mixture of E-isomer and Z-isomer is produced with E-isomer being dominant
Solution Approach 1:
The patent applies parameter changes by modifying the catalyst's ligand structure (using specific N-heterocyclic carbene ligands with particular substituents) to alter the reaction pathway and achieve Z-selectivity. This changes the chemical parameters of the catalyst system to favor Z-isomer formation while maintaining catalytic activity.
Solution Approach 2:
The patent employs composite catalyst systems combining metal centers (Ru, Mo, or W) with specifically designed N-heterocyclic carbene ligands containing oxygen and nitrogen donors. This composite structure creates a unique catalytic environment that enables high Z-selectivity through coordinated interaction between the metal and ligand components.
2Manufacturing precision
If conventional metathesis catalysts are used, then coupling reaction occurs, but Z-isomer selectivity is low
Solution Approach 1:
The patent modifies reaction parameters by using specific catalyst compositions with N-heterocyclic carbene ligands that have tailored electronic and steric properties. This parameter optimization enables the reaction to proceed efficiently while achieving high Z-selectivity, resolving the trade-off between productivity and precision.
Solution Approach 2:
The patent applies local quality by designing ligands with specific functional groups (oxygen and nitrogen donors) at particular positions around the metal center. This localized modification of the catalyst's chemical environment creates favorable conditions for Z-isomer formation without compromising overall reaction efficiency.
3Manufacturing precision
If alternative methods like Wittig chemistry are used, then internal olefins can be prepared, but the methods are not catalytic and/or not Z-selective
Solution Approach 1:
The patent transforms the reaction system from stoichiometric (Wittig) to catalytic by using metal-based catalysts with N-heterocyclic carbene ligands. This parameter change in the reaction mechanism enables both Z-selectivity and catalytic efficiency, overcoming the limitations of alternative methods.
Solution Approach 2:
The patent replaces the stoichiometric Wittig reagent mechanism with a catalytic metal-complex mechanism. This substitution changes the fundamental operating principle from consuming stoichiometric amounts of reagents to using catalytic amounts of metal complexes, improving both atom economy and Z-selectivity.
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
These catalysts achieve high Z-selectivity, with Z:E ratios greater than 1:1, enabling the efficient production of Z-isomers, which is essential for synthesizing valuable chemical products.
Implementation Method 1
Metathesis of a terminal olefin with itself produces ethylene and an internal olefin
Implementation Method 2
Carbon-carbon coupling reactions catalyzed by transition metal catalysts are among the most important reactions of synthetic organic chemistry
Data Source
AI summary
The present invention relates generally to catalysts and processes for the Z-selective formation of internal olefin(s) from terminal olefin(s) via homo-metathesis reactions.