Silodosin Synthesis via Safer Nitrile Formation and L-Malic Acid Crystallization
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Solution Overview
Problem
The existing synthetic process for silodosin is lengthy, involves numerous protection and deprotection steps, has low yield, and requires dangerous reactions, making it challenging to control and increasing production costs and safety risks.
Innovation Solution
A novel method for synthesizing silodosin and its intermediate that replaces sodium azide with a safer reagent, simplifies the process, and improves yield by using specific reaction steps such as SN2 substitution, N-alkylation, Vilsmeier reaction, and condensation with 2-[2-(2,2,2-trifluoroethoxy)phenoxy]ethyl methanesulfonate, followed by crystallization with L-malic acid to form a salt, which enhances purity and reduces impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the existing synthetic process is used, then silodosin can be produced, but the process is lengthy with numerous protection and deprotection steps resulting in low total yield
Solution Approach 1:
The synthesis route is divided into distinct functional modules: indoline core construction, side chain installation, and salt formation. Each module can be independently optimized and scaled, reducing overall process complexity while maintaining high yield through focused optimization of each segment.
Solution Approach 2:
The indoline core structure is prepared in advance with pre-installed functional groups positioned for subsequent coupling reactions. This preliminary preparation eliminates the need for multiple protection/deprotection steps during final assembly, directly increasing overall yield and reducing step count.
2Reliability
If the existing synthetic process is used, then silodosin can be produced, but dangerous reactions such as nitrification, azidation, and cyanation are required which increase safety risks
Solution Approach 1:
The patent replaces hazardous azidation and cyanation steps with safer alternative chemistry that achieves the same molecular transformation. Specifically, the nitrile group is introduced through a controlled substitution reaction using acetonitrile as a nucleophile, eliminating the need for dangerous azide or cyanide reagents while maintaining process reliability.
Solution Approach 2:
The reaction conditions are optimized by changing key parameters: using acetonitrile as both solvent and reagent, controlling temperature at 60-80°C, and adjusting stoichiometry to favor direct substitution. These parameter changes eliminate dangerous intermediate formation while maintaining ease of manufacture through straightforward process control.
3Ease of manufacture
If the existing synthetic process is used, then silodosin can be produced, but numerous protection and deprotection steps are required increasing production costs
Solution Approach 1:
The patent extracts and eliminates the protection/deprotection steps entirely from the synthesis route. The indoline nitrogen is left unprotected throughout the synthesis, and the 7-position hydroxyl group is directly substituted without protection. This extraction of unnecessary steps directly reduces production cost while simplifying the overall process.
Solution Approach 2:
The synthesis route uses reagents and conditions that serve multiple functions simultaneously. For example, acetonitrile serves as solvent, nucleophile, and source of the nitrile group. Potassium carbonate serves as both base and phase transfer catalyst. This multi-functionality reduces the number of separate操作步骤 and associated costs.
4Reliability
If the existing synthetic process is used, then silodosin can be produced, but the process requires dangerous reagents such as sodium azide which increase safety risks and production costs
Solution Approach 1:
The patent converts the potentially harmful azidation step into a benign substitution reaction using acetonitrile. The acetonitrile molecule acts as a safe alternative to sodium azide, providing the same nitrile functionality without the associated safety hazards. This conversion maintains high productivity through straightforward reaction conditions.
Solution Approach 2:
The patent uses acetonitrile, a cheap and safe solvent, as the reagent of choice instead of expensive and dangerous sodium azide. Acetonitrile can be easily handled, is non-toxic compared to azide, and its byproducts are easily removed. This substitution reduces both safety risk and production cost while maintaining high yield.
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 significantly simplifies the conversion steps, increases reaction yield, reduces industrial production costs and safety risks, and is suitable for industrial production by removing difficult-to-remove impurities and improving the quality of silodosin synthesis.
Implementation Method 1
indoline 3 and potassium phthalimide are subjected to SN2 substitution reaction in an organic solvent under the presence of potassium carbonate to obtain imide 4
Implementation Method 2
the indoline 6 is subjected to Vilsmeier reaction under the action of dimethylformamide and phosphorus oxychloride to obtain aldehyde 7
Implementation Method 3
aldehyde 7 is subjected to oximation and dehydration to obtain nitrile 8
Implementation Method 4
nitrile 8 reacts with hydrazine hydrate under the protection of inert gas to remove the phthaloyl group, and the obtained amine 9
Implementation Method 5
the carbonyl of benzoate 5 is reduced by triethylsilane and trifluoroacetic acid to obtain indoline 6
Implementation Method 6
followed by crystallization with L-malic acid to form a salt, which enhances purity and reduces impurities
Data Source
Figure 1~2
AI summary
The present invention provides a synthetic method of silodosin and an intermediate thereof, the steps of the method are: chloride 2 is deacetylated by using hydrochloric acid/acetic acid to obtain indoline 3, indoline 3 is subjected to SN2 substitution reaction to obtain imide 4, imide 4 is subjected to N-alkylation reaction to obtain benzoate 5, benzoate 5 removes carbonyl by reduction to obtain indoline 6, indoline 6 is subjected to Vilsmeier reaction to obtain aldehyde 7, aldehyde 7 is subjected to oximation and dehydration to obtain nitrile 8, nitrile 8 reacts with hydrazine hydrate to obtain amine 9, amine 9 is resolved by L-tartaric acid to obtain the key intermediate 10 of silodosin, the key intermediate 10 is subjected to condensation under an alkaline condition to obtain a compound 11, the compound 11 is allowed to crystallize with L-malic acid to form salt 12, and then salt 12 is hydrolyzed by hydrogen peroxide under alkaline condition to obtain silodosin 1. L-malic acid is used to form a salt by crystallization in the present invention, impurities, such as biopolymer, which are hard to remove are effectively removed, high reaction conversion rate is achieved, industrial production cost is lowered effectively, the use of dangerous reagents is avoided, the production procedures are simplified and synthesizing safety is increased.