Furanic Conversion to Phenols via Hydrazone Intermediates
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Solution Overview
Problem
Current methods for producing phenols and benzene carboxylic acids from fossil fuels are inefficient and require harsh conditions, leading to low yields and selectivity, while biomass-derived processes face challenges with furanic compounds' instability and complex reaction mixtures.
Innovation Solution
Converting the aldehyde group of furan carbaldehyde into a hydrazone or oxime group, reacting it with a dienophile, and subsequent hydrolysis and oxidation to produce phenolic or benzene carboxylic compounds, which enhances atom efficiency, selectivity, and yield, and allows for the use of inexpensive catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If furfural and 5-HMF are used directly in Diels-Alder reactions, then the process should be simpler, but harsh reaction conditions are required and the furanics decompose or polymerize
Solution Approach 1:
The patent applies preliminary action by converting the aldehyde group of furfural or 5-HMF into a hydrazone or oxime group before the Diels-Alder reaction. This pre-modification protects the furanic compound from decomposition and polymerization while enabling the reaction to proceed under milder conditions. The hydrazone/oxime group is subsequently restored after the Diels-Alder reaction, maintaining atom efficiency.
2Manufacturing precision
If furfural and 5-HMF are converted to furan or 2-MF before Diels-Alder reaction, then reactivity is improved, but additional reduction and oxidation steps are required
Solution Approach 1:
The patent uses hydrazone or oxime groups as intermediary protecting groups that temporarily modify the furanic compound to enable Diels-Alder reaction under milder conditions. These intermediaries are then restored to the original aldehyde functionality after the reaction, avoiding the need for separate reduction and oxidation steps while maintaining high selectivity.
Solution Approach 2:
The patent changes the chemical parameter of the furanic compound by converting the electron-withdrawing aldehyde group into an electron-neutral or electron-donating hydrazone/oxime group. This parameter change increases the reactivity of the furanic compound in Diels-Alder reactions and allows the reaction to proceed under milder conditions without requiring additional reduction and oxidation steps.
3Ease of manufacture
If conventional oxidation methods are used to convert biomass to furanics, then the process is established, but harsh conditions lead to low yields and selectivity
Solution Approach 1:
The patent applies preliminary action by modifying the furanic compound with hydrazone or oxime groups before the Diels-Alder reaction. This pre-protection strategy prevents decomposition and polymerization during the reaction, thereby improving yield and selectivity while maintaining process feasibility. The mild reaction conditions enabled by this preliminary action reduce side reactions and product loss.
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 achieves higher selectivity and yield with milder oxidation conditions, maintaining the carbonyl carbon atom in benzene carboxylic acids and producing phenols and benzene carboxylic acids efficiently from biomass-derived furanic compounds.
Implementation Method 1
converting the hydrazone or oxime into the corresponding phenol, carboxylic acid or ester thereof, through hydrolysis and oxidation
Implementation Method 2
converting the hydrazone or oxime into the corresponding phenol, carboxylic acid or ester thereof, through hydrolysis and oxidation
Implementation Method 3
reacting the thus obtained hydrazone or oxime with a dienophile, to form an aromatic hydrazone or oxime
Data Source
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AI summary
Described are methods for preparing phenols, benzene carboxylic acids, esters and anhydrides thereof from furanic compounds by reaction with a dienophile, wherein the furanic compounds are reacted with a hydrazine and/or oxime and then reacted with a dienophile.