Curtius Rearrangement Synthesis of Amine Intermediates
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Solution Overview
Problem
Current methods for synthesizing imatinib and nilotinib face challenges such as low yields, contamination with inorganic impurities, and the use of toxic or odorous chemicals, particularly in the reduction steps of the nitropyrimidine intermediate, which complicates large-scale manufacturing and purification.
Innovation Solution
A divergent synthesis route that bypasses late-stage reduction of the nitro group by converting a compound of Formula I into Formula III through acyl azide formation and Curtius rearrangement, using reagents like diphenylphosphoryl azide and nucleophilic attack with alcohols or water to form carbamates, which can be deprotected to obtain the desired amine intermediate efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the nitropyrimidine intermediate is reduced using traditional methods (palladium on carbon, stannous chloride), then the amine intermediate can be obtained, but the process generates inorganic impurities and requires additional purification steps
Solution Approach 1:
The invention extracts and removes the problematic reduction step entirely from the synthesis pathway. Instead of reducing the nitro group in the traditional manner, the patent uses a Curtius rearrangement of an acyl azide intermediate to directly generate the amine through a different mechanistic pathway, thereby extracting the source of inorganic impurities from the process
Solution Approach 2:
The invention introduces an acyl azide intermediate as a mediator between the carboxylic acid and the final amine product. This intermediary compound undergoes Curtius rearrangement to form an isocyanate, which then hydrolyzes to give the desired amine without requiring traditional reduction methods that generate inorganic impurities
2Ease of manufacture
If palladium catalysts are used for C-N bond formation and reduction steps, then the synthesis can proceed, but the cost of expensive ligands and catalysts increases
Solution Approach 1:
The invention extracts and eliminates the need for expensive palladium catalysts and ligands by replacing the traditional C-N bond formation and reduction sequence with a Curtius rearrangement pathway that uses inexpensive reagents such as diphenylphosphoryl azide and common solvents
Solution Approach 2:
The invention replaces expensive, reusable catalysts with inexpensive, single-use reagents. The acyl azide and diphenylphosphoryl azide are used in stoichiometric amounts and discarded after one use, but their low cost compared to palladium catalysts makes the overall process more economical
3Reliability
If the nitropyrimidine intermediate is synthesized and then reduced, then the amine intermediate can be obtained, but the process takes multiple steps and reduces overall efficiency
Solution Approach 1:
The invention merges the C-N bond formation and amine generation steps into a single integrated sequence. By forming the acyl azide intermediate and immediately subjecting it to Curtius rearrangement, the patent combines what were previously separate synthesis and reduction steps into one continuous process, improving overall productivity
Solution Approach 2:
The invention performs preliminary action by pre-forming the acyl azide intermediate with the nitropyrimidine compound, which then spontaneously undergoes Curtius rearrangement upon heating. This preliminary preparation eliminates the need for separate reduction steps and accelerates the overall synthesis process
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 provides a more efficient and scalable synthesis of imatinib and nilotinib by avoiding toxic reagents and improving yield and purity, reducing the need for costly metal catalysts and minimizing environmental impact.
Implementation Method 1
The acyl azide was formed by reacting the carboxylic acid with diphenylphosphoryl azide
Implementation Method 2
The acyl azide was then heated to effect a Curtius rearrangement to the isocyanate
Implementation Method 3
The isocyanate was then reacted with an alcohol or water to form the carbamate
Data Source
AI summary
Processes and useful intermediates for the synthesis of the tyrosine kinase inhibitors Formula (II) nilotinib and Formula (IV) imatinib. Key intermediates, method for their synthesis and their use in a divergent synthesis, making use of a Curtius rearrangement, to nilotinib and imatinib are described.