1-Alkyl-5-Hydroxypyrazole Direct Cyclization for High-Yield Production
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Solution Overview
Problem
Existing methods for producing 1-alkyl-5-hydroxypyrazoles are complex, yield low, and require expensive or difficult-to-produce raw materials, leading to inefficiencies and high costs.
Innovation Solution
A novel method using dialkylaminoacrylate ester and alkylhydrazine in a simplified reaction to produce 1-alkyl-5-hydroxypyrazole with high purity and yield, utilizing easily available and less expensive raw materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If method 1 (cyclization of dialkyl alkoxymethylenemalonate with alkylhydrazine) is used, then 1-alkyl-5-hydroxypyrazole can be produced, but the process requires multiple steps and complex separation procedures resulting in low yield
Solution Approach 1:
The patent segments the synthesis pathway by using dialkylaminoacrylate ester as a pre-functionalized starting material that contains the necessary structural elements for direct cyclization, eliminating the need for separate hydrolysis and decarboxylation steps required in conventional methods
Solution Approach 2:
The dialkylaminoacrylate ester is prepared in advance with the appropriate functional groups positioned for direct cyclization with alkylhydrazine, performing the structural preparation work before the final coupling reaction to improve efficiency
2Productivity
If method 2 (addition of hydrazine to acrylate ester followed by dehydration condensation with aldehyde) is used, then 1-alkyl-5-hydroxypyrazole can be produced, but the complex multi-step process produces many byproducts resulting in low yield
Solution Approach 1:
The patent extracts and eliminates the problematic intermediate steps (addition reaction followed by dehydration condensation) by using dialkylaminoacrylate ester that enables direct cyclization, removing the sources of byproduct formation
Solution Approach 2:
Instead of building the pyrazole ring through sequential reactions (addition then condensation then cyclization), the patent inverts the approach by using a pre-activated dialkylaminoacrylate ester that undergoes direct cyclization with alkylhydrazine in a single step
3Productivity
If method 3 (reaction of 3-alkoxyacrylate ester with alkylhydrazine) is used, then 1-alkyl-5-hydroxypyrazole can be produced in one step, but the raw material 3-alkoxyacrylate ester is difficult and expensive to produce
Solution Approach 1:
The patent replaces the expensive and difficult-to-produce 3-alkoxyacrylate ester with dialkylaminoacrylate ester, which is cheaper and easier to manufacture, sacrificing none of the one-step cyclization advantage
Solution Approach 2:
The patent changes the chemical parameters of the starting material from 3-alkoxyacrylate ester to dialkylaminoacrylate ester, modifying the functional group while maintaining the ability to undergo direct cyclization with alkylhydrazine
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
The method achieves a high-yield, high-purity production of 1-alkyl-5-hydroxypyrazole suitable for agricultural herbicides, reducing complexity and cost through a simpler process.
Implementation Method 1
a dialkylaminoacrylate ester and an alkylhydrazine are reacted to thereby produce a 1-alkyl-5-hydroxypyrazole
Data Source
AI summary
The present invention provides a production method that can easily produce a 1-alkyl-5-hydroxypyrazole by subjecting a dialkylaminoacrylate ester and an alkylhydrazine to a reaction as represented by the following reaction formula A. (Reaction formula A) (In the formula, R1, R2, and R3 are each independently a C1 to C6 alkyl group, R4 is a hydrogen atom, a C1 to C6 alkyl group, a C2 to C6 alkenyl group, a C3 to C6 cycloalkyl group, or an aryl group, which groups are optionally substituted with halogen, a hydroxy group, an alkoxy group, or a C1 to C6 alkyl group.)