Anagrelide Synthesis via Imine Reduction and In-Situ Salt Formation
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Solution Overview
Problem
Current processes for producing anagrelide and its analogues are inefficient, requiring multiple synthetic steps, leading to low yields and stability issues due to the use of hazardous reagents and complex purification processes, with challenges in scalability and environmental impact.
Innovation Solution
A two-step process involving the reaction of a glycine derivative with a compound in the presence of a base and solvent to form an imine, followed by reduction with sodium borohydride or sodium triacetoxyborohydride, which eliminates the need for hazardous reagents and reduces the number of purification steps, using cheaper solvents like toluene and optimizing yield and batch cycle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional multi-step process with cyanogen bromide is used to prepare anagrelide hydrochloride, then the product can be obtained, but the yield decreases over time due to competing acid hydrolysis and the process requires time-consuming reflux steps
Solution Approach 1:
The patent extracts and eliminates the problematic cyanogen bromide step from the synthesis pathway. Instead of using cyanogen bromide to form the iminoquinazoline intermediate, the invention uses a different route that avoids this hazardous reagent and the subsequent acid hydrolysis issues, thereby improving both reliability and productivity
Solution Approach 2:
The patent replaces the expensive and hazardous cyanogen bromide reagent with more stable, commercially available alternatives. The new methodology uses disposable, stable intermediates that do not require stringent handling conditions, reducing both cost and production time while eliminating yield degradation issues
2Ease of operation
If the hydrochloride monohydrate salt form is prepared through reflux with hydrochloric acid, then solubility is improved, but the process is time-consuming and yield decreases due to competing acid hydrolysis reactions
Solution Approach 1:
The patent performs preliminary salt formation during the cyclization step itself, rather than requiring a separate post-reaction salt formation step. The hydrochloride salt is formed in-situ as the iminoquinazoline cyclizes, eliminating the need for time-consuming reflux with hydrochloric acid and preventing subsequent acid hydrolysis of the lactam ring
Solution Approach 2:
The patent merges the cyclization step and salt formation step into a single operational step. By adding hydrochloric acid during the cyclization reaction rather than after, the process combines two separate operations into one, reducing overall processing time and eliminating the need for prolonged reflux
3Manufacturing precision
If multiple purification steps are implemented to ensure product purity, then the purity of anagrelide is improved, but the complexity and cost of production increase
Solution Approach 1:
The patent designs a self-purifying reaction system where the product crystallizes directly from the reaction mixture in high purity form. The reaction conditions are optimized so that anagrelide hydrochloride precipitates as the desired salt form, automatically separating from impurities without requiring complex purification equipment or multiple processing steps
Solution Approach 2:
The patent optimizes reaction parameters including solvent composition, temperature, and acid concentration to control product crystallization. By adjusting these parameters, the reaction produces high-purity product that can be isolated by simple filtration, eliminating the need for complex chromatography or recrystallization procedures
4Productivity
If hazardous reagents like cyanogen bromide are used in the synthesis, then the reaction proceeds efficiently, but environmental impact and safety concerns increase
Solution Approach 1:
The patent converts the harmful cyanogen bromide reagent into a beneficial alternative pathway. Instead of using the hazardous cyanogen bromide, the invention employs safe, environmentally friendly reagents that achieve the same chemical transformation through a different mechanism, thereby maintaining reaction efficiency while eliminating environmental and safety hazards
Solution Approach 2:
The patent introduces a safe intermediary compound that replaces cyanogen bromide in the synthesis pathway. This intermediary serves the same functional role of forming the iminoquinazoline ring but does so through a safer, more environmentally acceptable chemical transformation that avoids the release of toxic byproducts
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 enhances the yield and purity of anagrelide and its analogues, reduces the complexity and cost of production, and minimizes the need for hazardous reagents, making it more commercially viable and environmentally friendly.
Implementation Method 1
reducing the imine compound of formula (XII) with a suitable reducing agent to form the compound of formula (A)
Data Source
AI summary
The present invention relates to a novel process for producing anagrelide, 6,7-dichloro-1,5- dihydroimidazo [2,1-b] quinazolin 2 (3H)-one, or certain analogues thereof. The process of the invention also provides improved processes for producing key intermediates required for the synthesis of anagrelide or certain analogues thereof.