Indomethacin Intermediate Purification with THF-Alcohol Crystallization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing synthetic processes for Indomethacin fail to adequately control impurities such as 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 key intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide, ultimately impacting the final product's impurity profile.

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

VSEngineering 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

Engineering Contradiction:

Improveimpurity controlVSAvoidproduction efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent applies parameter changes by modifying the solvent system from conventional single solvents to a specific mixture of tetrahydrofuran and C1-C4 alkyl alcohol. This parameter change in the crystallization process enables selective precipitation of the key intermediate with significantly reduced impurity content (below 0.15% each for Impurity C and F), thereby improving manufacturing precision without substantially compromising productivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes phase transitions through controlled crystallization and precipitation processes. By adjusting temperature and solvent composition parameters, the key intermediate is induced to precipitate in a purified crystalline form, separating it from impurities that remain in the mother liquor. This phase transition approach achieves high purity (impurities < 0.15%) while maintaining efficient production through optimized crystallization conditions

Inventive Principle:

Principle #36Phase transitions

2Ease of manufacture

If the key intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide is used with typical impurity levels (1%-15%), then the synthesis process is simple, but the final Indomethacin product quality and impurity profile are compromised

Engineering Contradiction:

Improveprocess simplicityVSAvoidintermediate purity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies the extraction principle by selectively removing impurities from the key intermediate through precipitation and crystallization processes. The solvent mixture of tetrahydrofuran and C1-C4 alkyl alcohol selectively dissolves the key intermediate while leaving impurities (Impurity C and F) in the mother liquor, achieving separation and purification without complex additional steps

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent implements preliminary action by performing purification of the key intermediate through controlled precipitation and crystallization before proceeding to the final Indomethacin synthesis. This preliminary purification step ensures that impurities are removed early in the process (reducing them to below 0.15%), preventing their carry-forward to the final product and eliminating the need for extensive downstream purification

Inventive Principle:

Principle #10Preliminary action

3Productivity

If impurities are not controlled in the key intermediate, then the process is faster and simpler, but the reproducibility and quality control of the final product are affected

Engineering Contradiction:

Improveprocess speedVSAvoidproduct reproducibility

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies feedback principles by establishing controlled precipitation and crystallization parameters that consistently achieve impurity reduction to below 0.15%. The specific solvent ratio, temperature profile, and addition rate are optimized to provide reproducible purification results, ensuring that every batch of key intermediate meets the specified purity criteria before proceeding to final synthesis

Inventive Principle:

Principle #23Feedback

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 significantly lowers the content of impurities in the intermediate and final Indomethacin, ensuring high purity and improved process control, aligning with regulatory standards.

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

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 2

Methodology Applied

Scientific EffectPrecipitation: Precipitation

Data Source

PatentUS20250263373A1Process for the preparation of indomethacin

Publication Date: 2025.08.21 F I S FAB ILTALIANA SINTETICI SPA

AI summary

An improved process for the preparation of Indomethacin of formula (I):is provided by means of the precipitation, crystallization, re-crystallization or re-slurry of the intermediate 4-chloro-N-(4-methoxyphenyl)benzohydrazide in a mixture containing tetrahydrofuran and a C1-C4 linear or branched alkyl alcohol.