1,2-Benzisothiazolin-3-One Synthesis With Low Thioether By-Products
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Solution Overview
Problem
Existing processes for preparing 1,2-benzisothiazolin-3-one are time-consuming, costly, and produce significant amounts of by-products like thioethers and mercapto compounds, making them inefficient and economically unviable.
Innovation Solution
A process involving the reaction of a 2-halobenzonitrile with a mixture of alkali metal sulfide and an alkyl halide, followed by reaction with a halogenating agent or oxidizing agent, to form 1,2-benzisothiazolin-3-one, minimizing by-product formation and enabling reuse of alkyl halides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a 2-halobenzonitrile is reacted with an alkyl thiol to form a 2-(alkylthio)benzonitrile and then reacted with a halogenating agent, then 1,2-benzisothiazolin-3-one is obtained, but large amounts of volatile by-products and unutilizable thioethers are generated
Solution Approach 1:
The invention changes the reaction parameters by using a specific molar ratio of reactants (2-halobenzonitrile to alkyl thiol between 1:0.8 to 1:1.2) and controlling the reaction conditions (temperature, solvent system) to optimize the formation of 1,2-benzisothiazolin-3-one while minimizing by-product formation. This parameter optimization directly addresses the contradiction by improving yield while reducing substance loss.
Solution Approach 2:
The invention recovers and reuses the alkyl halide by-product from the reaction. The alkyl halide generated during the reaction is separated and fed back into the reaction system as a reactant, transforming what would be waste into a valuable resource. This recovery process directly reduces substance loss while maintaining high productivity.
2Productivity
If existing processes are used to prepare 1,2-benzisothiazolin-3-one, then the product is obtained, but the processes are time-consuming and costly
Solution Approach 1:
The invention performs preliminary action by pre-mixing the 2-halobenzonitrile and alkyl thiol in optimized ratios before initiating the reaction with halogenating agent. This preparation step ensures that when the reaction starts, all components are ready to react efficiently, reducing overall reaction time and improving productivity without sacrificing product quality.
Solution Approach 2:
The invention implements continuous reaction conditions where the halogenating agent is added gradually to maintain continuous formation of the desired product. The reaction is conducted in a continuous manner with steady-state conditions, eliminating idle time between steps and maximizing productive action throughout the process.
3Productivity
If existing processes are used to prepare 1,2-benzisothiazolin-3-one, then the product is obtained, but the processes are economically unviable
Solution Approach 1:
The invention recovers the alkyl halide by-product and reuses it as a reactant in the next reaction cycle. This recovery eliminates the need to purchase fresh alkyl halide for each batch, significantly reducing material costs and improving economic viability while maintaining high production efficiency.
Solution Approach 2:
The reaction system is designed to be self-sufficient by generating its own reactants. The alkyl halide produced during the reaction serves as the reactant for the next batch, making the process self-service and reducing external material inputs, thereby improving economic viability.
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 process achieves high yields of 1,2-benzisothiazolin-3-one with reduced by-product formation, particularly thioethers, and allows for the direct reuse of alkyl halides, enhancing economic viability and efficiency.
Implementation Method 1
reaction of a 2-halobenzonitrile compound with a reaction mixture comprising alkali metal sulfide and/or alkali metal hydrogensulfide and an alkyl halide compound to form an intermediate
Implementation Method 2
reaction of the intermediate with a halogenating agent or an oxidizing agent to form the 1,2-benzisothiazolin-3-one
Implementation Method 3
reaction of the intermediate with a halogenating agent or an oxidizing agent to form the 1,2-benzisothiazolin-3-one
Data Source
AI summary
The invention relates to a process for preparing 1,2′-benzisothiazoline-3-one according to formula (I), comprising the following steps: (a) reacting a 2-halogenbenzonitrile compound of general formula (II) with a reaction mixture, containing: (i) alkaline sulphide and/or alkaline hydrogen sulphide and (ii) an alkyl halide compound, represented by general formula (III): R1X (III) for producing an intermediate product of general formula (IV), and (b) reacting the intermediate product of general formula (V) obtained in step (a) with a halogenating agent or an oxidant and subsequent reaction of the 2-(alkylsulfoxy)benzonitrile with an acid to form 1,2-benzisothiazoline-3-one as well as a halide compound of general formula (V) R1X (V).