Direct Atipamezole Hydrochloride Crystallization from Aqueous Acid
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Solution Overview
Problem
The existing methods for preparing atipamezole hydrochloride require isolating the atipamezole base before converting it to its hydrochloride salt, which is inefficient and involves the use of solvents like methylene chloride and ethyl acetate.
Innovation Solution
A method that directly isolates crystalline atipamezole hydrochloride from an aqueous solution through hydrogenation in hydrochloric acid, concentrating, cooling, and crystallizing, without the need for intermediate base isolation and using alternative solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the conventional method of isolating atipamezole base before converting to hydrochloride salt is used, then the product can be obtained, but the process is inefficient and requires multiple solvents (methylene chloride and ethyl acetate)
Solution Approach 1:
The patent merges the hydrogenation step and the salt formation step into a single integrated process. The atipamezole base is hydrogenated directly in the presence of hydrochloric acid, so that the free base is immediately converted to its hydrochloride salt during the reaction, eliminating the need for separate isolation and conversion steps
Solution Approach 2:
The patent removes the intermediate isolation of atipamezole base from the process entirely. By conducting hydrogenation in aqueous hydrochloric acid solution, the base is never isolated - it is directly converted to the hydrochloride salt form, taking out the unnecessary intermediate step and associated solvents
2Ease of manufacture
If methylene chloride and ethyl acetate solvents are used for isolation and conversion, then atipamezole hydrochloride can be obtained, but the process becomes less economical and more complex
Solution Approach 1:
The patent changes the solvent system from organic solvents (methylene chloride, ethyl acetate) to an aqueous hydrochloric acid solution. This parameter change in the solvent medium allows the reaction and crystallization to proceed directly in water, eliminating the need for organic solvent extraction and conversion steps
Solution Approach 2:
The patent uses hydrochloric acid as an intermediary that serves multiple functions: it provides the acidic environment for hydrogenation, supplies the chloride ions for salt formation, and acts as the solvent medium throughout the process, eliminating the need for separate solvent systems
3Loss of time
If intermediate base isolation is performed, then conversion to hydrochloride salt is possible, but processing time increases and yield is reduced
Solution Approach 1:
The patent establishes continuous useful action by maintaining the atipamezole in solution throughout the entire process. The hydrogenation, salt formation, and crystallization occur in sequence without isolating the intermediate base, keeping the material continuously in a usable form and minimizing processing time and losses
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 is more efficient and economical, eliminating the need for solvent use and directly producing crystalline atipamezole hydrochloride, with improved yield and reduced processing time.
Implementation Method 1
hydrogenation of compound of formula (II) or a salt thereof in aqueous solution of hydrochloric acid under catalyst
Implementation Method 2
hydrogenation of compound of formula (II) or a salt thereof in aqueous solution of hydrochloric acid under catalyst
Implementation Method 3
cooling the concentrated solution; and recovering crystallized atipamezole hydrochloride
Data Source
AI summary
A method of isolating atipamezole hydrocloride as a crystalline salt is provided.