HBED Synthesis via Reductive Amination
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Solution Overview
Problem
Current methods for producing N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED) and its derivatives are complex, involve toxic reagents like cyanides, and suffer from low yields and the formation of byproducts, making large-scale industrial production challenging.
Innovation Solution
A process involving reductive amination of glyoxylic acid with a salan compound in the presence of an amine proton acceptor, using catalytic hydrogenation and easily available reagents, which allows for the preparation of HBED and its derivatives in a simplified reaction system without the need for toxic cyanides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods using disodium N,N'-ethylenediaminediacetate and o-acetoxybenzyl bromide are used, then HBED can be synthesized, but the process becomes complex requiring multiple steps and toxic cyanides
Solution Approach 1:
The synthesis is divided into two independent stages: first preparing N,N'-bis(2-hydroxybenzyl)ethylenediamine from ethylenediamine and salicylaldehyde, then converting it to HBED through reductive amination with glyoxylic acid. This segmentation eliminates the need for complex protecting group chemistry and cyanide-based carboxymethylation.
Solution Approach 2:
The patent converts the previously harmful cyanide-based carboxymethylation step into a beneficial reductive amination process using glyoxylic acid and hydrogen gas. The harmful toxic reagent (cyanide) is replaced by benign reagents (glyoxylic acid, H2 gas with catalyst), turning a harmful process into a safe and efficient one.
2Reliability
If conventional methods are used, then HBED can be prepared, but toxic reagents like cyanides must be employed
Solution Approach 1:
The patent converts the previously harmful cyanide-based carboxymethylation step into a beneficial reductive amination process using glyoxylic acid and hydrogen gas. The harmful toxic reagent (cyanide) is replaced by benign reagents (glyoxylic acid, H2 gas with catalyst), turning a harmful process into a safe and efficient one.
Solution Approach 2:
The patent uses inexpensive, readily available reagents such as ethylenediamine, salicylaldehyde, glyoxylic acid, and common catalysts like Raney nickel or Pd/C. These replace expensive and hazardous reagents like cyanides and acetoxybenzyl bromide, making the process both safer and more economically viable for industrial scale-up.
3Reliability
If conventional multi-step methods are used, then HBED can be synthesized, but the number of steps increases and yields decrease
Solution Approach 1:
The synthesis is divided into two independent stages: first preparing N,N'-bis(2-hydroxybenzyl)ethylenediamine from ethylenediamine and salicylaldehyde, then converting it to HBED through reductive amination with glyoxylic acid. This segmentation eliminates the need for complex protecting group chemistry and cyanide-based carboxymethylation.
Solution Approach 2:
The patent performs preliminary condensation of ethylenediamine with salicylaldehyde to form the salen complex, which is then directly reduced and subjected to reductive amination in subsequent steps. This preliminary action simplifies the overall pathway by pre-organizing the molecular structure for the final HBED formation, reducing the total number of steps required.
4Reliability
If conventional methods are used, then HBED can be prepared, but byproducts are formed reducing purity
Solution Approach 1:
The patent converts the previously harmful cyanide-based carboxymethylation step into a beneficial reductive amination process using glyoxylic acid and hydrogen gas. The harmful toxic reagent (cyanide) is replaced by benign reagents (glyoxylic acid, H2 gas with catalyst), turning a harmful process into a safe and efficient one.
Solution Approach 2:
The patent employs controlled reaction parameters including specific pH ranges (pH 7-9 for condensation, pH 2-3 for reductive amination), temperature control (reflux conditions), and catalyst selection to optimize reaction specificity. These parameter changes minimize side reactions and byproduct formation, ensuring high product purity.
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 process reduces the number of steps, eliminates the use of toxic cyanides, and achieves higher yields, making it suitable for industrial-scale production of HBED and its derivatives under standard conditions.
Implementation Method 1
reductive amination of glyoxylic acid with a salan compound of formula (II) in the presence of an amine proton acceptor
Implementation Method 2
using catalytic hydrogenation and easily available reagents
Data Source
AI summary
The invention relates to a process for the preparation of N,N'-bis(2-hydroxybenzyl)-ethylenediamine-N,N'-diacetic acid and its derivatives of general formula I, wherein both R have the same meaning and are selected from H, C1-C4alkyl, CH2OH, SO3M, and COOM; and all M have the same meaning and represent hydrogen atom, Na, K or NH4; which comprises reductive amination of glyoxylic acid with a salan compound of general formula (II), in the presence of an amine proton acceptor. The compounds of formula (I) can be used as chelating agents for micronutrients in fertilizer preparations for plants.