2-Alkyl-3-Aminothiophene Synthesis via Nitro Group Inversion
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Solution Overview
Problem
Current methods for producing 2-alkyl-3-aminothiophene are inefficient due to the instability of 3-aminothiophene derivatives, require protective group manipulation, and have low yields with difficulties in handling and separating position isomers, making them costly and operationally challenging.
Innovation Solution
A method involving the oxidation and reduction of specific compounds represented by Formulas (1) to (4) to produce 2-alkyl-3-aminothiophene derivatives, utilizing halogenating or esterifying agents, and reacting with α-mercaptoacetaldehyde or 1,4-dithian-2,5-diol to achieve the desired product, thereby bypassing the need for protective groups and improving operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a 3-aminothiophene derivative is produced by reacting with a carbonyl compound and then reducing, then the product can be obtained, but the process requires protective group manipulation which reduces operational efficiency and increases cost
Solution Approach 1:
The patent extracts the problematic amino group from the reaction sequence by using a nitro group instead. The nitro group serves as a protected form of the amino group that can be introduced and manipulated without requiring additional protective group steps, then converted to the amino group in a final reduction step.
Solution Approach 2:
Instead of directly introducing the amino group and then protecting it, the patent inverts the approach by first introducing the nitro group (which inherently serves as protection) and then converting it to the amino group at the end. This reversal eliminates the need for separate protective group manipulation steps.
2Productivity
If 3-nitrothiophene is produced by nitrating thiophene, then the starting material can be obtained, but the yield is low due to position isomers and separation is required
Solution Approach 1:
The patent introduces a substituent at the 2-position of the thiophene ring that creates electronic or steric differentiation, making the 3-position uniquely reactive toward nitration. This local modification ensures that nitration occurs exclusively at the desired position, eliminating isomer formation and the need for separation.
Solution Approach 2:
The patent performs preliminary substitution at the 2-position before nitration to pre-determine the reaction site. This preliminary action directs the subsequent nitration to occur only at the 3-position, preventing isomer formation before it can occur.
3Productivity
If 2-alkyl-3-nitrothiophene derivative is reduced to produce 2-alkyl-3-aminothiophene, then the final product can be obtained, but the starting material is difficult to produce
Solution Approach 1:
The patent segments the synthesis into distinct stages: first forming the 2-substituted thiophene with appropriate directing groups, then nitrating at the 3-position, and finally reducing the nitro group. This segmentation allows each step to be optimized independently, making the overall process more efficient.
Solution Approach 2:
The patent uses the 2-substituent as an intermediary that directs the nitration reaction to the 3-position. This intermediary group facilitates the selective formation of the desired isomer, which can then be converted to the final product through reduction.
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 efficiently produces 2-alkyl-3-aminothiophene with enhanced operational efficiency and cost-effectiveness by eliminating the need for protective group manipulation and improving yield, making it suitable for industrial use as an intermediate in agricultural and medical products.
Implementation Method 1
oxidizing a compound represented by the following Formula (1) to produce a compound represented by the following Formula (3)
Implementation Method 2
reducing the compound represented by the following Formula (3)... as it is known that a nitro group can be converted to an amino group through a reduction reaction
Data Source
AI summary
The present invention provides a method of producing 2-alkyl-3-aminothiophene derivative represented by Formula (4), the method comprising oxidizing a compound represented by the following Formula (1) to produce a compound represented by the following Formula (3) and reducing the compound represented by the following Formula (3):wherein in Formula (1), Formula (3), and Formula (4), R represents an alkyl group, a cycloalkyl group, or a bicycloalkyl group; and X represents a hydroxyl group, a halogen atom acyloxy group, an alkylsulfonyl group, or an arylsulfonyl group.