Dithiolate-Ligated Ru Catalyst for E-Macrocycle Synthesis
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Solution Overview
Problem
Current methods for synthesizing E-macrocycles using stereoretentive ruthenium olefin metathesis catalysts face challenges with low yields and slow catalyst initiation, particularly when reacting with E-olefins, leading to inefficient production of E-macrocycles with high selectivity.
Innovation Solution
The use of stereoretentive ruthenium olefin metathesis catalysts supported by dithiolate ligands, specifically catalyst 4, which exhibits faster initiation and higher activity, allowing for the synthesis of E-macrocycles with exceptional selectivity (>99% E) from diene starting materials bearing two E-olefins, resulting in higher yields and shorter reaction times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If stereoretentive ruthenium olefin metathesis catalysts are used for E-macrocycle synthesis, then E-selectivity is improved (>99% E), but yield is reduced and reaction time is increased
Solution Approach 1:
The patent modifies catalyst parameters by changing the ligand structure from conventional phosphine or NHC ligands to dithiolate ligands (specifically S-Ad and S-Bn variants). This parameter change in the catalyst's chemical structure fundamentally alters its reactivity profile, enabling fast initiation with E-olefins while maintaining stereoretention. The dithiolate ligands create a unique electronic and steric environment at the ruthenium center that accelerates the rate-determining initiation step without compromising E-selectivity.
Solution Approach 2:
The patent creates composite catalyst systems by combining ruthenium centers with dithiolate ligand frameworks. These composite structures integrate the stabilizing effect of chelating dithiolate ligands with the reactivity of ruthenium olefin metathesis catalysts. The resulting composite catalysts exhibit synergistic properties: the dithiolate ligands provide structural stability and tune the electronic properties, while the ruthenium center maintains catalytic activity, achieving both high productivity and high E-selectivity.
2Speed
If conventional Ru-olefin metathesis catalysts are used, then catalyst initiation is slow with E-olefins, but if modified catalysts are used, then initiation speed is improved
Solution Approach 1:
The patent changes the ligand parameter from conventional phosphine or NHC ligands to dithiolate ligands, which fundamentally alters the catalyst's initiation behavior. The dithiolate ligands modify the electronic density and steric environment at the ruthenium center, creating a more reactive species that initiates faster with E-olefins. This parameter change transforms the rate-determining step without requiring complex multi-component systems.
3Loss of time
If stereoretentive catalysts are used for macrocycle synthesis, then reaction time is reduced, but yield remains moderate to high only under optimized conditions
Solution Approach 1:
The patent optimizes reaction parameters by combining the dithiolate-ligated ruthenium catalyst with specific solvent choices and temperature conditions. These parameter optimizations create a reaction environment that maximizes both rate and yield. The dithiolate catalyst's inherent fast initiation is further enhanced by selecting solvents that stabilize the transition state and temperatures that balance kinetics with equilibrium considerations.
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
Catalyst 4 achieves significant improvements in yield and reaction time for E-macrocycle synthesis, producing 12- to 18-membered macrocycles, including recifeiolide, with high E-selectivity and moderate to high yields (47%-80%), overcoming previous limitations in E-selective cross metathesis.
Implementation Method 1
ring-closing metathesis (RCM) has gained widespread use in organic synthesis for the production of macrocyclic frameworks
Implementation Method 2
This transition metal-catalyzed reaction is commonly used in the synthesis of many biologically active compounds
Data Source
AI summary
This invention relates generally to the synthesis of E-macrocycles using stereoretentive ruthenium olefin metathesis catalysts supported by dithioiate ligands. Macrocycles were generated with excellent selectivity (>99% E) and in moderate to high/good yields (47% to 80% yield; 58% to 80% yield) from diene starting materials bearing two E-olefins or bearing one E-olefin and one terminal olefin, A variety of rings were constructed, ranging from 12- to 18-membered macrocycles, including the antibiotic recifeiolide. The invention has utility in the fields of organometallics and organic synthesis.