Pyrazole Synthesis Yield and Purification
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Solution Overview
Problem
Existing methods for preparing 5-alkylthioethylamino-1-phenyl-pyrazoles suffer from low yields and require extensive and costly purification processes to achieve high purity samples.
Innovation Solution
A process involving the reaction of 5-amino-1-phenyl-pyrazole with an alkylthioalkylchloride in the presence of a basic potassium salt and a nitrile solvent at controlled temperatures, significantly increasing yields and simplifying purification by reducing side products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing methods using bases like sodium hydride and solvents like tetrahydrofuran, dimethylformamide or dioxane are used to prepare 5-alkylthioethylamino-1-phenyl-pyrazoles, then the reaction can proceed, but the yields are low (10-39%) and extensive purification work is required
Solution Approach 1:
The patent changes the chemical parameters by selecting specific bases (potassium carbonate, potassium fluoride, tripotassium phosphate) and solvents (acetonitrile, propionitrile) that create optimal reaction conditions. This parameter optimization increases yields to 70-80% and dramatically reduces side products, eliminating the need for extensive purification work and making the process economically feasible for large-scale production
Solution Approach 2:
The patent replicates the successful combination of base and solvent parameters from laboratory scale to industrial scale (10-100 g and more). By copying the optimized conditions that achieve >95% purity through simple column chromatography or recrystallisation, the process becomes economically viable for large-scale production without requiring complex HPLC separation
2Manufacturing precision
If existing methods are used to prepare high purity samples of 5-alkylthioethylamino-1-phenyl-pyrazoles, then some product is obtained, but the purification process is difficult and expensive
Solution Approach 1:
The patent optimizes reaction parameters by using potassium-based bases (carbonate, fluoride, or tripotassium phosphate) in nitrile solvents (acetonitrile, propionitrile) at controlled temperatures (20-100°C) for 1-8 hours. This parameter set minimizes side product formation and enables achievement of >95% purity through simple recrystallisation or column chromatography, avoiding expensive HPLC separation
Solution Approach 2:
The patent employs inexpensive purification methods (recrystallisation, column chromatography) that can achieve high purity without requiring expensive, complex equipment like HPLC systems. The simple workup procedures using readily available materials make the process economically feasible for producing large quantities of high purity compound
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 achieves yields above 70% and allows for the purification of high-purity 5-alkylthioethylamino-1-phenyl-pyrazoles, making large-scale production economically feasible with minimal need for advanced purification techniques.
Implementation Method 1
5-amino-1-phenyl-pyrazole (II) is reacted with an alkylthioalkylchloride (III) preferably with 2-alkylthioethylchloride (R3-S-CH2-CH2-Cl), in the presence of a base comprising a basic potassium salt
Implementation Method 2
in a solvent comprising a nitrile or a mixture of nitriles, preferably in a nitrile e.g. selected from the group consisting of acetonitrile, propionitrile or a mixture thereof, preferably at a temperature between 20-100°C
Data Source
AI summary
The invention relates to a process for the preparation of 5-alkylthioethylamino-1-phenyl-pyrazoles of formula (I) and the preparation of 5-methylamino-1-phenylpyrazole intermediates.