Perfuming Intermediate Synthesis via Cross Metathesis for Z-Selectivity
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Solution Overview
Problem
Existing methods for producing (Z)-2-(pent-2-en-1-yl)cyclopent-2-en-1-one, a key perfuming ingredient, are costly and involve the use of toxic reagents like bromine and require complex steps such as Wittig reactions.
Innovation Solution
A cross metathesis reaction between commercially available compounds of formulas (II) and (III), followed by basic treatment and a [1,5]hydrogen shift, to produce (Z)-2-(pent-2-en-1-yl)cyclopent-2-en-1-one using a metathesis catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Wittig reaction or selective hydrogenation is used to prepare (Z)-2-(pent-2-en-1-yl)cyclopent-2-en-1-one, then the target compound can be obtained, but expensive starting materials and expensive conditions are required
Solution Approach 1:
The patent changes the reaction parameters by using cross-metathesis conditions with specific catalysts (Ru, Mo, W, or Re-based) instead of Wittig or hydrogenation conditions. This parameter change enables the use of cheaper starting materials (compounds of formulas II and III) while maintaining the ability to obtain the target compound with high Z-selectivity
Solution Approach 2:
The patent employs readily available, inexpensive starting materials (compounds of formulas II and III) that can be obtained from commercial sources, replacing expensive specialized reagents. The process uses catalytic amounts of metal complexes rather than stoichiometric amounts of expensive reagents, making the overall process more cost-effective
2Reliability
If 1,4-dibromo-2-pentene is used as starting material, then (Z)-2-(pent-2-en-1-yl)cyclopent-2-en-1-one can be prepared via addition and [1,5]hydrogen shift, but highly toxic bromine is required
Solution Approach 1:
The patent eliminates the need for toxic bromine by using cross-metathesis reaction that directly forms the desired carbon-carbon double bond. The harmful bromination step is replaced with a benign metathesis reaction using catalytic metal complexes, converting a harmful process into a beneficial and safe one
Solution Approach 2:
The patent introduces metal complex catalysts (Ru, Mo, W, or Re-based) as intermediaries to facilitate the cross-metathesis reaction between compounds of formulas II and III. These catalysts mediate the formation of the target compound without requiring toxic bromine, providing a clean and efficient reaction pathway
3Reliability
If protection/deprotection steps are included in the synthesis route, then the target compound can be obtained with proper functional group protection, but the process becomes more complex
Solution Approach 1:
The patent extracts and eliminates the unnecessary protection/deprotection steps from the synthesis route. By carefully selecting starting materials (compounds of formulas II and III) that are compatible with cross-metathesis conditions, the method directly produces the target compound without requiring additional protection steps, thereby simplifying the overall process
4Ease of manufacture
If cross metathesis reaction is used between compounds of formulas (II) and (III), then a cost-effective and straightforward approach is achieved, but high selectivity for Z stereochemistry must be ensured
Solution Approach 1:
The patent optimizes reaction parameters including catalyst selection (Ru, Mo, W, or Re-based metal complexes), catalyst loading (0.01-10 mol%), temperature (25-100°C), and solvent choice to achieve high Z-selectivity. By carefully controlling these parameters, the cross-metathesis reaction produces the desired Z-isomer with high stereoselectivity while maintaining cost-effectiveness
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 method provides a straightforward and selective access to (Z)-2-(pent-2-en-1-yl)cyclopent-2-en-1-one, avoiding toxic reagents and reducing production costs.
Implementation Method 1
by cross metathesis between compound of the formulae (II) with compound of formula (III) in the presence of a metathesis catalyst
Implementation Method 2
followed by basic treatment and followed by a [1,5]hydrogen shift
Data Source
AI summary
The present invention relates to the field of organic synthesis and more specifically it concerns a process for preparing compound of formula (I) by a cross metathesis reaction. Said compound of formula (I) is valuable new chemical intermediate for producing perfuming ingredients and is also part of the present invention.