Continuous-Flow Diclofenac Sodium Preparation via Microchannel Reactors

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Solution Overview

Problem

Conventional batch reactor methods for preparing diclofenac sodium are hindered by lengthy reaction times, low yields, high labor intensity, and safety concerns due to the use of toxic and corrosive materials, leading to environmental pollution and limited industrial suitability.

Innovation Solution

A continuous-flow reaction system utilizing microchannel reactors and sequential units for amidation, condensation, chlorination, Friedel-Crafts alkylation, and hydrolysis reactions, which enhances mass and heat transfer, suppresses side reactions, and allows for continuous operation without catalyst separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional batch reactor methods are used for preparing diclofenac sodium, then the synthesis can be performed with readily available raw materials, but the reaction time is lengthy and the yield is low

Engineering Contradiction:

Improvereaction timeVSAvoidyield

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces conventional batch mechanical stirring and heating systems with a continuous-flow microchannel reaction system. This substitution enables precise control of reaction parameters, enhanced mass and heat transfer, and significantly reduced reaction time while improving yield through continuous operation and optimized flow conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements continuous-flow reaction methodology where reactants continuously flow through microchannel reactors, eliminating the start-stop nature of batch processing. This continuous operation maintains optimal reaction conditions throughout the process, preventing side reactions and maximizing yield while reducing total reaction time.

Inventive Principle:

Principle #20Continuity of useful action

2Manufacturing precision

If toxic and corrosive materials such as oxalyl chloride, diazomethane, or sodium cyanide are used in the synthesis, then the yield of diclofenac sodium can be improved, but severe environmental pollution and safety hazards occur

Engineering Contradiction:

ImproveyieldVSAvoidenvironmental pollution

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent converts potentially harmful reagents into safer alternatives that maintain or improve yield. Specifically, it replaces toxic oxalyl chloride with less hazardous acylating agents, substitutes explosive diazomethane with safer carbon sources, and replaces highly toxic sodium cyanide with alternative carbonation methods, thereby eliminating severe environmental pollution while preserving high yields.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent employs readily available, less toxic raw materials that can be used in continuous-flow processes without requiring complex handling procedures. This approach uses simpler, safer reagents that achieve the same synthetic objectives without the environmental and safety burdens of traditional toxic materials.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of manufacture

If multiple reaction steps including Ullmann condensation, decarboxylation, acylation, cyclization, hydrolysis, and salt formation are performed, then the synthesis can be achieved with conventional methods, but the process becomes lengthy and complex

Engineering Contradiction:

Improvesynthesis feasibilityVSAvoidreaction time

Core Design Contradiction:

Ease of manufactureVSLoss of time

Solution Approach 1:

The patent merges multiple conventional reaction steps into a continuous-flow sequence where intermediates are directly transferred between reaction zones without isolation. This integration of Ullmann condensation, decarboxylation, acylation, cyclization, hydrolysis, and salt formation into a streamlined continuous process eliminates time-consuming workup and purification steps between reactions.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent performs preliminary actions by pre-mixing reactants and preparing flow conditions before entering the microchannel reactors. This preliminary preparation ensures that all subsequent reactions proceed under optimal conditions from the start, reducing the time required for each step and eliminating the need for extensive intermediate adjustments.

Inventive Principle:

Principle #10Preliminary action

4Ease of operation

If conventional batch processing with catalyst separation is used, then the reaction can be performed with standard equipment, but labor intensity is high and automation is difficult

Engineering Contradiction:

Improveoperation simplicityVSAvoidautomation level

Core Design Contradiction:

Ease of operationVSExtent of automation

Solution Approach 1:

The continuous-flow system enables uninterrupted operation where reactants continuously flow through reaction and separation zones. This continuity eliminates the need for manual catalyst separation and product isolation between batches, allowing full automation of the process from feedstock to final product with minimal human intervention.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The system incorporates self-service features where the continuous-flow microchannel reactors and integrated separation units automatically perform reaction, separation, and purification functions without manual catalyst removal or product isolation steps. The process self-regulates through continuous flow control, enabling high automation levels.

Inventive Principle:

Principle #25Self-service

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 reduces reaction time, improves yield and purity of diclofenac sodium, enhances process efficiency, and reduces labor and energy consumption, making it more suitable for industrial production.

Implementation Method 1

Methodology Applied

Scientific EffectMass transfer: Diffusion

Implementation Method 2

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS11834388B2Continuous-flow preparation method of diclofenac sodium

Publication Date: 2023.12.05 FUDAN UNIVERSITY

AI summary

This application relates to pharmaceutical engineering, and more particularly to a continuous-flow preparation method of diclofenac sodium. The continuous-flow preparation method includes: subjecting aniline and chloroacetic acid to amidation to obtain 2-chloro-N-phenylacetamide (3); subjecting 2-chloro-N-phenylacetamide (3) and 2,6-dichlorophenol to continuous condensation to obtain N-(2,6-dichlorophenyl)-2-hydroxy-N-phenylacetamide (5); subjecting N-(2,6-dichlorophenyl)-2-hydroxy-N-phenylacetamide (5) and thionyl chloride to chlorination to obtain N-(2,6-dichlorophenyl)-2-chloro-N-phenylacetamide (6); subjecting N-(2,6-dichlorophenyl)-2-chloro-N-phenylacetamide (6) to Friedel-Crafts alkylation in the presence of aluminum chloride to obtain 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indol-2-one (7); and subjecting 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indol-2-one (7) to hydrolysis to obtain the diclofenac sodium.