4-(4-Fluorobenzylamino)-1-Methylpiperidine Trihydrate Crystallization
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Solution Overview
Problem
Existing processes for preparing 4-(4-fluorobenzylamino)-1-methylpiperidine result in sub-optimal purity due to unreacted starting materials and under- or over-reduced addition products, making it difficult to remove impurities effectively.
Innovation Solution
The preparation of 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate, which is a solid and crystalline form, achieved by treating 4-(4-fluorobenzylamino)-1-methylpiperidine with water, thereby improving stability and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If 4-(4-fluorobenzylamino)-1-methylpiperidine is prepared using existing reductive amination processes, then the product can be obtained, but the purity is sub-optimal due to unreacted starting materials and under- or over-reduced addition products
Solution Approach 1:
The patent changes the physical state parameter of the product from liquid to solid crystalline form by forming a trihydrate salt. This parameter change enables effective purification through crystallization, resolving the contradiction between achieving high purity and the difficulty of removing impurities from the liquid form.
Solution Approach 2:
The patent utilizes phase transition from liquid to solid crystalline form through hydrate formation. The solid crystalline trihydrate can be purified by filtration and washing, whereas the liquid form cannot be purified by recrystallization, thus resolving the purification difficulty.
2Productivity
If 4-(4-fluorobenzylamino)-1-methylpiperidine is used directly without purification, then the production process is simpler, but the impurities affect the final pimavanserin product quality
Solution Approach 1:
The patent performs preliminary purification by converting the liquid intermediate to its solid crystalline trihydrate form, which can then be filtered and washed to remove impurities before the pimavanserin-forming reaction. This preliminary purification action ensures high purity of the final product while maintaining production efficiency.
3Manufacturing precision
If 4-(4-fluorobenzylamino)-1-methylpiperidine is converted to dihydrochloride salt for purification, then the purity is improved, but an additional conversion step is required
Solution Approach 1:
The patent changes the counterion parameter from chloride (dihydrochloride) to water (trihydrate). This parameter change maintains the purification benefit of salt formation while eliminating the need for subsequent base treatment to regenerate the free amine, thus reducing the number of process steps.
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 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate demonstrates improved stability and purity, allowing it to be used directly in the pimavanserin-forming reaction without the need for additional purification steps, thus enhancing the overall efficiency and yield of the pimavanserin production process.
Implementation Method 1
The preparation of 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate, which is a solid and crystalline form, achieved by treating 4-(4-fluorobenzylamino)-1-methylpiperidine with water
Data Source
AI summary
This invention relates to 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate and a process for the preparation of 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate comprising treating 4-(4-fluorobenzylamino)-1-methylpiperidine with water.The invention also relates to a process for the preparation of pimavanserin comprising reacting 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate with 1-isobutoxy-4-(isocyanatomethyl) benzene; to a process for the preparation of a pimavanserin acid addition salt comprising reacting 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate with 1-isobutoxy-4-(isocyanatomethyl) benzene and converting pimavanserin into a pimavanserin acid addition salt, pimavanserin and pimavanserin acid addition salts obtainable by the process, and to the use of 4-(4-fluorobenzylamino)-1-methylpiperidine trihydrate for preparing pimavanserin or an acid addition salt thereof.