Regioselective Chlorination of Indoline-2,3-dione
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Solution Overview
Problem
Current methods for synthesizing 5-chloro-7-methylindoline-2,3-dione suffer from low regioselectivity and yield, leading to the production of multiple byproducts and the need for costly fractional distillation, making them inefficient for the manufacture of the agrochemical insecticide chlorantraniliprole.
Innovation Solution
A one-pot process involving sequential cyclization and chlorination of 2-hydroxyimino-N-(o-tolyl)acetamide in a mixture of sulfuric acid and acetic acid, followed by the addition of sulfur dioxide and chlorine gas, which facilitates the direct formation of 5-chloro-7-methylindoline-2,3-dione with high regioselectivity and yield without the need for intermediate isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chlorination of N-(2-methylphenyl)acetamide is performed using conventional methods, then the reaction proceeds, but the regioselectivity is low (61%) and multiple byproducts are formed
Solution Approach 1:
The patent changes the reaction parameters by using a specific solvent system (acetic acid with catalytic sulfuric acid) and controlling temperature (50-60°C) to achieve high regioselectivity (95%+) for the desired 5-chloro-7-methylindoline-2,3-dione product, eliminating the need for fractional distillation
Solution Approach 2:
The patent uses acetic acid as an intermediary solvent system that facilitates the cyclization and chlorination reactions in sequence, enabling the transformation of N-(2-methylphenyl)-2-(hydroxyimino)acetamide to the desired chlorinated indoline-2,3-dione with high regioselectivity without requiring intermediate isolation
2Manufacturing precision
If fractional distillation is used to purify the desired product, then regioselective purity (95%+) is achieved, but the process becomes costly and complex
Solution Approach 1:
The patent extracts the purification step by designing a reaction system that directly produces the desired product with high regioselectivity (95%+) without requiring fractional distillation, thereby simplifying the process and reducing costs while maintaining product purity suitable for chlorantraniliprole manufacture
3Productivity
If conventional chlorination methods are used, then the reaction proceeds, but the yield is low and the process is inefficient
Solution Approach 1:
The patent merges the cyclization and chlorination reactions into a single one-pot process using acetic acid as the solvent system, allowing sequential transformation of N-(2-methylphenyl)-2-(hydroxyimino)acetamide to 5-chloro-7-methylindoline-2,3-dione with high yield and efficiency without requiring intermediate isolation or multiple reaction vessels
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 achieves high yields and regioselective purity of 5-chloro-7-methylindoline-2,3-dione, eliminating the need for intermediate isolation and reducing byproduct formation, thereby providing a cost-effective and efficient route for producing the desired agrochemical intermediate.
Implementation Method 1
Initial cyclization is carried out in a mixture of sulfuric acid and acetic acid
Implementation Method 2
followed by reaction with sulfur dioxide and chlorine gas to directly yield 5-chloro-7-methylindoline-2,3-dione
Implementation Method 3
followed by reaction with sulfur dioxide and chlorine gas
Data Source
AI summary
A one-pot process for the manufacture of 5-chloro-7-methylindoline-2,3-dione starting from 2-hydroxyimino-N-(2-methylphenyl)acetamide via tandem cyclization in sulfuric acid and acetic acid, followed by in-situ chlorination with sulfur dioxide and chlorine gas in high regioselectivity and yield.