Indomethacin Intermediate Crystallization for Impurity Control
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Solution Overview
Problem
Existing synthetic processes for Indomethacin do not adequately control the impurities 4-chloro-N-(4-methoxyphenyl) benzamide (Impurity C) and 4-chloro-N'-(4-chlorobenzoyl)-N-(4-methoxyphenyl)benzo hydrazide (Impurity F), which are typically present in 1%-15% and affect the reproducibility and quality of the final product.
Innovation Solution
A process involving precipitation, crystallization, re-crystallization, or re-slurry of the intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide in a mixture of tetrahydrofuran and a C1-C4 linear or branched alkyl alcohol, followed by conversion to Indomethacin, effectively reducing impurities to below 0.15% each.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional synthetic processes are used to prepare Indomethacin, then the production efficiency is maintained, but the impurity content (Impurity C and Impurity F) remains high at 1%-15%, affecting product quality and reproducibility
Solution Approach 1:
The patent applies preliminary action by performing purification of the intermediate compound (4-chloro-N-(4-methoxyphenyl)benzohydrazide) before the final conversion to Indomethacin. The purification step removes Impurity C and Impurity F from the intermediate, ensuring that when the intermediate is subsequently converted to Indomethacin, the final product has controlled impurity levels. This preliminary purification action prevents impurity carry-forward and enables both high product quality and maintained productivity.
Solution Approach 2:
The patent employs parameter changes by optimizing crystallization conditions including solvent selection (water, ethanol, isopropanol, or their mixtures), temperature control (cooling rates and final temperatures), and pH adjustment during the purification process. These parameter optimizations enable effective separation of the intermediate from Impurities C and F through controlled crystallization, achieving both high purity intermediate (low impurity content) and efficient production.
2Manufacturing precision
If the intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide is used directly without purification, then the production process is simple and fast, but the impurity profile of the final Indomethacin product is poor
Solution Approach 1:
The patent applies phase transitions by utilizing controlled crystallization of the intermediate compound from solution. The process involves dissolving the crude intermediate in appropriate solvents (water, ethanol, isopropanol, or their mixtures) and then cooling the solution to induce selective crystallization of the pure intermediate, leaving Impurities C and F in the mother liquor. This phase transition approach provides an efficient purification mechanism that is relatively simple to implement while achieving high final product purity.
Solution Approach 2:
The patent uses solvent systems (water, ethanol, isopropanol, or their mixtures) as intermediaries to facilitate the purification process. These solvents mediate the separation between the intermediate compound and Impurities C and F through differential solubility and crystallization behavior. The choice of solvent or solvent mixture acts as an intermediary that enables effective purification without requiring complex equipment or multiple processing 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
The process significantly lowers the content of impurities C and F in the intermediate and final Indomethacin, ensuring high purity and reproducibility by controlling the impurity profile.
Implementation Method 1
precipitation, crystallization, re-crystallization, or re-slurry of the intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide in a mixture of tetrahydrofuran and a C1-C4 linear or branched alkyl alcohol
Implementation Method 2
precipitation, crystallization, re-crystallization, or re-slurry of the intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide in a mixture of tetrahydrofuran and a C1-C4 linear or branched alkyl alcohol
Data Source
AI summary
Object of the present invention is an improved process for the preparation of Indomethacin of formula (I): by means of the precipitation, crystallization, re-crystallization or re-slurry of the intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide in a mixture comprising tetrahydrofuran and a C1-C4 linear or branched alkyl alcohol.