Pyrazole Alkylation Isomer Conversion via Acid Catalysis
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Solution Overview
Problem
The production of N-alkylated substituted pyrazoles, such as ethyl 3-(difluoromethyl)-1-methyl-1 H-pyrazole-4-carboxylate, faces challenges in achieving high yields of the non-iso isomer, leading to increased costs and wastage in commercial fungicide production.
Innovation Solution
A process involving the reaction of a mixture comprising a compound of formula I and a compound of formula IV with a compound of formula III or IIIA in the presence of an acid, which catalyzes the conversion of the iso isomer to the non-iso isomer, thereby increasing the proportion of the desired non-iso isomer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If regioselective N-alkylation of substituted pyrazoles is achieved by reacting with trialkyl phosphates or trialkylphosphonates, then the non-iso isomer can be produced, but the yield of the non-iso isomer is insufficient leading to increased costs and wastage
Solution Approach 1:
The patent applies parameter changes by introducing acid catalysts (such as sulfuric acid, polyphosphoric acid, or Lewis acids) to change the reaction conditions. This catalytic approach enables the rapid conversion of the iso isomer to the non-iso isomer, thereby improving the yield of the desired non-iso isomer while maintaining the regioselective N-alkylation process using trialkyl phosphates or trialkylphosphonates
2Productivity
If the iso isomer is rapidly converted into the non-iso isomer by use of an acid, then the yield of the non-iso isomer increases, but additional reagents and process steps are required
Solution Approach 1:
The patent uses acid catalysts as intermediaries to facilitate the isomerization reaction. The acid (such as sulfuric acid, polyphosphoric acid, or Lewis acids like BF3·OEt2 or AlCl3) acts as a mediator that enables the rapid conversion of the iso isomer to the non-iso isomer without being consumed in the reaction, thus improving yield while adding minimal complexity to the process
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 process effectively increases the yield of the non-iso isomer, reducing production costs and wastage by promoting thermodynamic equilibrium between the iso and non-iso isomers, making the production more efficient and cost-effective.
Implementation Method 1
the invention relates to the isomerisation of N-alkylated substituted pyrazoles... the iso isomer may be rapidly converted into the non-iso isomer by use of an acid
Data Source
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AI summary
The present invention relates to processes for the preparation of a compound of formula (I) comprising reacting a compound of formula (IV) with a compound of formula III or (IIIA) in the presence of an acid; wherein R1 is C1-C4 haloalkyl; R2 is optionally substituted alkyl, optionally substituted aryl or optionally substituted heteroaryl; R3 is methyl or ethyl; R4 is hydrogen, optionally substituted alkyl, optionally substituted aryl or optionally substituted heteroaryl; and n is 0 or 1.