Asymmetric Azine Synthesis via In-Situ Hydrazone Precipitation
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Solution Overview
Problem
The existing methods for producing asymmetric azine compounds with polar groups, such as hydroxyl or carboxyl groups, face challenges due to high water solubility of hydrazone intermediates, leading to low yields and difficulties in isolation, especially when using excess hydrazine and acid-promoted disproportionation reactions.
Innovation Solution
Reacting hydrazine and benzaldehyde with an acidic group at a 1:1 molar ratio in an alcohol solvent to precipitate a hydrazone compound, then adding 4-hydroxybenzaldehyde without isolating the hydrazone, allowing the asymmetric azine compound to preferentially precipitate and be isolated by filtration, thereby improving selectivity and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large excess of hydrazine is used to react with aldehyde in alcohol solvent, then the hydrazone compound can be formed, but the hydrazone compound has high water solubility making it difficult to isolate from the reaction system
Solution Approach 1:
The patent applies preliminary action by first forming the hydrazone compound with high water solubility in alcohol solvent, then subsequently adding a second aldehyde to convert it to the azine compound. This sequence allows the intermediate to remain in solution during formation but precipitate as the final product, solving the isolation difficulty without requiring premature separation
Solution Approach 2:
The patent changes the chemical parameters of the reaction system by introducing a second aldehyde compound that reacts with the hydrazone intermediate. This parameter change transforms the soluble hydrazone into the insoluble azine compound, enabling easy filtration and isolation while maintaining high yield
2Productivity
If the hydrazone compound is not isolated and a second aldehyde is added directly, then the process becomes more efficient, but disproportionation reaction is promoted by acid reducing the yield
Solution Approach 1:
The patent implements continuity of useful action by performing the reaction in two continuous steps without isolating the intermediate. The hydrazone compound formed in the first step immediately reacts with the second aldehyde in the same reaction mixture, maintaining continuous productive action while avoiding isolation losses and time
Solution Approach 2:
The patent uses the hydrazone compound as an in-situ intermediary that mediates the transformation from first aldehyde to asymmetric azine. By keeping this intermediary in solution and allowing it to react further, the process maintains high efficiency while the final azine product's low solubility prevents disproportionation and enables easy separation
3Manufacturing precision
If protecting groups are used to protect polar groups, then reaction selectivity can be improved, but production cost increases due to expensive protecting groups
Solution Approach 1:
The patent extracts the need for protecting groups entirely from the synthesis pathway. By designing a reaction sequence where the polar groups remain unprotected throughout both steps, the method eliminates the costly protection and deprotection steps while maintaining high selectivity through the specific reactivity sequence of hydrazone formation followed by azine formation
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 enables the production of a highly pure asymmetric azine compound with high selectivity and yield, avoiding the issues of low yield and isolation difficulties associated with previous methods, and is industrially advantageous by eliminating the need for expensive protecting groups.
Implementation Method 1
reacting hydrazine and benzaldehyde that has an acidic group (e.g., hydroxyl group or carboxyl group) at the 4-position in a molar ratio of 1:1 in an alcohol solvent to precipitate a hydrazone compound
Implementation Method 2
the target asymmetric azine compound preferentially precipitates from the reaction system with the progress of the reaction. These findings have led to the completion of the present invention.
Data Source
AI summary
Disclosed are a novel asymmetric azine compound (I) and a method for producing an asymmetric azine compound (I) which is characterized in that an aldehyde compound (III) and hydrazine are reacted in an alcohol solvent at a molar ratio (aldehyde compound (III)):(hydrazine) of from 2:1 to 1:2, thereby obtaining a reaction solution including a hydrazone compound (IV), and then an aldehyde compound (V) is added for a reaction into the thus-obtained reaction solution at a molar ratio (aldehyde compound (V) ):(hydrazone compound (IV)) of from 2:1 to 1:2. The method can commercially advantageously produce an asymmetric azine compound having a polar group such as a hydroxyl group or a carboxyl group in each molecule. The novel asymmetric azine compound can be obtained by this production method. (In the formulae, R1 and R2 each represents a hydroxyl group or a carboxyl group, X1 to X8 each represents a hydrogen atom, -C(=O)-OR3 or the like; and R3 represents an alkyl group having 1 to 10 carbon atoms or the like.)