Amide Synthesis via Acylpyridinium Intermediates

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Solution Overview

Problem

The symmetric acid anhydride method has low reactivity with amines of low nucleophilicity, leading to slow coupling reactions, while the mixed acid anhydride method produces undesired ester byproducts due to reactions with counter anions.

Innovation Solution

A method involving the dehydration and condensation of carboxylic acids to form acid anhydrides, which are then reacted with a base to produce a cationically active species, such as acylpyridinium, that reacts efficiently with amines to form amides, minimizing side reactions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If symmetric acid anhydride is used as activation agent, then the structure is simple and production cost is low, but the reactivity with amine is weak causing slow coupling reaction

Engineering Contradiction:

Improvestructure simplicity and production costVSAvoidcoupling reaction speed

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent employs mixed acid anhydride instead of symmetric acid anhydride, creating an asymmetric structure with different acyl groups. This asymmetry provides different reactivity characteristics, allowing one acyl group to be highly reactive toward amines while the other provides stability, thus resolving the contradiction between structural simplicity and reaction speed.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the chemical parameters of the activation agent by using mixed acid anhydride with specific acyl group combinations. This parameter change optimizes the balance between reactivity and stability, enabling faster coupling reactions while maintaining manageable structural complexity.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If mixed acid anhydride is used to increase reactivity, then coupling reaction proceeds faster, but ester byproducts are produced due to reaction with counter anions

Engineering Contradiction:

Improvecoupling reaction speedVSAvoidester byproduct production

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potential harmful reaction between acylpyridinium species and counter anions into a beneficial pathway by designing the mixed acid anhydride system where the less reactive acyl group preferentially reacts with counter anions to form stable byproducts, while the highly reactive acyl group couples with amines to form desired amide bonds.

Inventive Principle:

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

Solution Approach 2:

The patent applies different functional characteristics to different parts of the mixed acid anhydride molecule. One acyl group is designed to be highly reactive toward amines for efficient coupling, while the other acyl group has moderated reactivity that directs it toward counter anion reaction, thereby localizing the harmful side reaction away from the desired amide bond formation.

Inventive Principle:

Principle #3Local quality

3Productivity

If highly active activation agent is used, then coupling reaction is fast, but isomerization and byproduct production increase

Engineering Contradiction:

Improvecoupling reaction speedVSAvoidisomerization and byproduct control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent segments the activation function into two separate acyl groups within the mixed acid anhydride structure. This segmentation allows one group to handle the activation and coupling function with high reactivity, while the other group manages the side reaction control, thereby dividing the conflicting requirements and achieving both fast reaction and high precision.

Inventive Principle:

Principle #1Segmentation

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 achieves high reaction efficiency and reduces the occurrence of side reactions, enabling rapid and effective amide bond formation even with amines of low nucleophilicity, and minimizes byproduct production.

Implementation Method 1

comprises dehydrating and condensing carboxylic acids;

Methodology Applied

Scientific EffectDehydration condensation:

Implementation Method 2

reacting the dehydrated and condensed carboxylic acids with any one or more base, which is then reacted with an amine simultaneously

Methodology Applied

Scientific EffectAcylpyridinium formation:

Implementation Method 3

a coupling reaction between the acylpyridinium species and an amine is performed to obtain an amide

Methodology Applied

Scientific EffectNucleophilic acyl substitution:

Data Source

PatentEP3808758B1Method for producing amide

Publication Date: 2023.10.25 YOKOGAWA ELECTRIC CORP

Figure 1

AI summary

A method for producing an amide includes: dehydrating and condensing carboxylic acids and then reacting them with a base, and reacting them with an amine.