Macrocyclic Musk Synthesis via Cross Metathesis
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Solution Overview
Problem
The existing methods for synthesizing macrocyclic musk compounds, particularly through ring closure metathesis, face challenges such as catalyst-induced double bond migration, differences in reactivity of olefin groups leading to poor yields, and the complexity of separating and isolating desired products from mixtures of homo- and heterodimers, making the process inefficient and costly for industrial scalability.
Innovation Solution
A method involving cross metathesis reaction using homogeneous transition metal catalysts with alkylidene ligands to form heterodimers, which are then cyclized to produce macrocyclic musk compounds, allowing for higher yields and easier separation of products, and eliminating the need for high dilution conditions, thus making the process more economically viable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If ring closure metathesis is used to form macrocyclic structures, then cyclic products are obtained, but intra-molecular ring closing competes with intermolecular polymerisation requiring high dilution conditions
Solution Approach 1:
The patent inverts the conventional approach by performing intermolecular cross-metathesis first to form heterodimers, then inducing intramolecular cyclization in a second step. This reversal eliminates the need for high dilution conditions during the primary reaction, allowing concentrated conditions that improve productivity while avoiding polymerization side reactions.
Solution Approach 2:
The patent segments the macrocyclization process into two distinct stages: (1) cross-metathesis of diene substrates to form heterodimer intermediates, and (2) subsequent cyclization to form the final macrocyclic product. This segmentation allows each step to be optimized independently, with the first step proceeding under concentrated conditions for high efficiency.
2Productivity
If cross metathesis is used to couple olefin substrates, then heterodimers are formed, but complex mixtures of homo-dimers and hetero-dimers are produced that are difficult to separate
Solution Approach 1:
The patent introduces distinct functional groups at the termini of the diene substrates (e.g., ester groups with different alkyl chains) that create local chemical differences between the two olefin components. These local quality differences result in heterodimers with unique physical properties (boiling points, polarities) that facilitate easy separation from homo-dimer by-products through standard purification techniques.
Solution Approach 2:
The patent employs parameter changes in the substrate design, specifically varying the chain length and structure of ester groups attached to the diene substrates. This creates measurable parameter differences (molecular weight, polarity) between heterodimer and homo-dimer products, enabling efficient separation by distillation or chromatography.
3Adaptability or versatility
If different olefin groups are used in cross metathesis, then desired heterodimers are formed, but differences in reactivity lead to poor yields
Solution Approach 1:
The patent optimizes reaction parameters including catalyst selection (Grubbs first or second generation), temperature control, and substrate concentration to balance the reactivity differences between diverse olefin groups. By adjusting these parameters, the patent achieves high conversion rates and yields while maintaining the ability to use structurally diverse diene substrates with different functional groups.
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 results in an efficient and high-yielding synthesis of macrocyclic musk compounds and their open-chain intermediates, facilitating industrial scalability by simplifying the process and reducing costs through the use of higher concentrations and the elimination of solvents, thereby overcoming the limitations of traditional ring closure metathesis.
Implementation Method 1
A variant of olefin metathesis - so-called cross metathesis - is the reaction of two different olefins in the presence of an organometallic catalyst, in which one olefin double bond changes places with the other. More particularly, it is an organic reaction that entails the redistribution of fragments of olefins by the scission and regeneration of carbon-carbon double bonds.
Implementation Method 2
The mechanism of this reaction is thought to proceed via a 2+2 cycloaddition of an alkene-bearing substrate to a metal alkylidene catalyst, forming a metallocyclobutane intermediate, which undergoes cycloreversion to generate the substrate loaded with a metal carbene, which further reacts with a second alkene to produce the metathesis product
Implementation Method 3
cyclizing the hetero-dimer intermediate to form the macrocyclic musk compound
Data Source
AI summary
A method of forming a macrocyclic musk compound comprising the steps of:- i) cross-metathesizing a first olefin and a second olefin in the presence of a homogeneous transition metal catalyst comprising an alkylidene ligand, to form a statistical mixture of a hetero-dimer intermediate of said first and second terminal olefin, and homo-dimers ii) separating the hetero-dimer from the statistical mixture of hetero-and homo- dimers iii) and cyclizing the hetero-dimer intermediate to form the macrocyclic musk compound.