One-Pot Synthesis of Dichloropyridazine Amines
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Solution Overview
Problem
Current processes for preparing pyridazine amine compounds, particularly dichloropyridazine amines, face challenges such as low yields, harsh reaction conditions, and the need for irritant starting materials like 3,4,5-trichloropyridazine, which complicates industrial applications and requires laborious work-ups.
Innovation Solution
A process involving a one-pot reaction where a compound of formula II is reacted with POCl3, followed by an amine compound, allowing in situ formation of 3,4,5-trichloropyridazine, which is then used to produce dichloropyridazine amines without the need for isolating the irritant intermediate, and a hydrogenation/dehalogenation step in the absence of a base to achieve high yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 3,4,5-trichloropyridazine is used as starting material for nucleophilic substitution, then dichloropyridazine amine compounds can be prepared, but the process requires handling irritant compounds and involves laborious work-ups
Solution Approach 1:
The patent performs the dehalogenation reaction before the nucleophilic substitution reaction, converting 3,4,5-trichloropyridazine to 3,5-dichloropyridazine in advance. This preliminary action eliminates the need to handle large amounts of the irritant 3,4,5-trichloropyridazine during the main synthesis process, as only small amounts are needed for the in situ generation of the intermediate
Solution Approach 2:
The patent uses 3,5-dichloropyridazine as an in situ generated intermediate that mediates between the starting material and final product. By generating this intermediate during the reaction process rather than isolating it, the patent avoids the need to handle and purify the irritant trichloro compound separately
2Productivity
If traditional dehalogenation processes are used, then dichloropyridazine amines can be obtained, but yields are low and reaction conditions are harsh
Solution Approach 1:
The patent combines multiple reactions (dehalogenation and nucleophilic substitution) into a continuous one-pot process where the output of the first reaction directly feeds the second reaction without isolation. This continuous action maintains high concentrations of reactive intermediates and eliminates time losses, achieving high yields under mild conditions
Solution Approach 2:
The patent merges the dehalogenation reaction and nucleophilic substitution reaction into a single combined process. By merging these two previously separate steps, the patent eliminates the need for harsh isolation conditions and achieves high yields through the synergistic effect of continuous reaction
3Manufacturing precision
If multiple separate reaction steps are used, then each transformation can be optimized, but the overall process becomes complex and requires laborious work-ups
Solution Approach 1:
The patent merges dehalogenation, intermediate formation, and nucleophilic substitution into a single integrated reaction process. This merging maintains manufacturing precision by optimizing all steps simultaneously in one pot, while dramatically reducing process complexity by eliminating multiple isolation and purification steps
4Reliability
If base is added to avoid catalyst poisoning from HCl production, then dehalogenation can proceed, but the process becomes more complex and requires additional work-up steps
Solution Approach 1:
The patent skips the traditional step of adding base to neutralize HCl by conducting the dehalogenation reaction under conditions where HCl management is simplified. The process rushes through the reaction quickly enough that HCl does not accumulate to poisoning levels, or is managed in situ without requiring additional base addition and subsequent neutralization work-up steps
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 simplifies the process, eliminates the need for harsh conditions, and achieves high yields of dichloropyridazine amines, facilitating industrial scalability and reducing the handling of irritant compounds.
Implementation Method 1
dehalogenation of dichloropyridazine amine compounds can be performed by a hydrogenation/dehalogenation reaction in the presence of hydrogen and a hydrogenation catalyst
Implementation Method 2
The art suggests that this hydrogenation/dehalogenation of pyridazine amine compounds is performed in the presence of a base. It is disclosed that HCl produced from dechlorination tends to be absorbed on the activated carbon, leading to a progressive poisoning of Pd/C
Data Source
AI summary
Provided herein is a process for preparing a pyridazine amine compound of formula V, and a process for preparing dichloropyridazine amine compounds of formula IVa, IVb, and mixtures thereof. Further, provided herein are dichloropyridazine amine compounds of formula IVa, IVb, and mixtures thereof, wherein the amino group is an ethylamino group.