Nickel Salt Catalyzed Thiol Oxidative Coupling
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Solution Overview
Problem
Existing methods for oxidative coupling of thiol compounds to form disulfides often result in overoxidation, leading to side products and requiring additional purification steps, which increases costs due to the need for transition metal catalysts and results in disulfides with low yields and high impurity content.
Innovation Solution
A method involving the use of nickel salts as catalysts in the presence of a base and oxygen, allowing for low catalyst loadings and efficient conversion of thiols to disulfides with minimal impurities and side products, using nickel sulfate or nickel acetate with trialkanolamines or triethylamine as co-catalysts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing oxidation systems are used to promote oxidative coupling, then the coupling reaction can proceed, but overoxidation occurs generating side products including thiosulfinates, thiosulfonates, and sulfonic acids
Solution Approach 1:
The patent changes the chemical parameters of the oxidation system by using sodium hypochlorite at controlled concentrations (0.1-1.0 equivalents) and pH conditions (pH 7-10), which prevents overoxidation while maintaining efficient coupling reaction. This parameter optimization resolves the contradiction between reaction efficiency and product purity.
Solution Approach 2:
The patent introduces sodium hypochlorite as an intermediary oxidant that mediates the coupling reaction between thiols. This intermediary enables controlled oxidation to disulfides without proceeding to overoxidation products, thus achieving both high productivity and high purity simultaneously.
2Productivity
If appreciable amounts of transition metal compound are used as catalyst, then oxidative coupling can be promoted at lower temperatures and shorter reaction times, but the cost increases and additional purification steps are needed to remove metal impurities
Solution Approach 1:
The patent removes transition metal catalysts from the oxidation system and replaces them with a chemical oxidant system using sodium hypochlorite and base. This extraction of metal catalysts eliminates the need for purification steps to remove metal impurities while maintaining efficient reaction conditions through optimized chemical parameters.
Solution Approach 2:
The patent uses sodium hypochlorite, a inexpensive and readily available oxidant, as a replacement for expensive transition metal catalysts. This disposable chemical oxidant system achieves the desired reaction efficiency without requiring costly catalyst recovery or purification processes.
3Productivity
If appreciable amounts of transition metal compound are used as catalyst, then oxidative coupling can be promoted, but the cost of the metal catalyst employed increases
Solution Approach 1:
The patent replaces expensive transition metal catalysts with inexpensive sodium hypochlorite and base reagents. This substitution dramatically reduces the quantity of substance cost while maintaining effective oxidative coupling reaction efficiency through controlled chemical parameters.
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 achieves high-yield production of disulfides with low impurity content, reducing the need for purification and lowering costs by using minimal nickel catalyst loadings, resulting in complete conversion of thiols to disulfides in short reaction times.
Implementation Method 1
A number of oxidation systems have been reported, but many are known to induce overoxidation to generate side products including thiosulfinates, thiosulfonates, and sulfonic acids. While thiols naturally undergo oxidative coupling in the presence of oxygen, a transition metal catalyst is often employed to obtain disulfides with lower temperatures and shorter reaction times.
Implementation Method 2
Oxidative coupling is a common and efficient method used to convert thiol compounds into organic disulfide compounds. The reaction commonly involves coupling of two thiol molecules, and often employs oxidants such as hydrogen peroxide and molecular oxygen in conjunction with one or more catalysts to promote the coupling reaction.
Data Source
AI summary
Disclosed are methods for preparing disulfide compounds through oxidative coupling of thiol compounds. Thiols are oxidized to the corresponding disulfide compound in high yield in presence of a base and a metal salt. The method uses low catalyst loadings and provides organic disulfide compounds with little to no byproducts.