Iridium Catalyst Asymmetric Hydrogenation of Imines
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Solution Overview
Problem
Existing catalyst systems for asymmetric hydrogenation of imines face challenges such as deactivation, low productivity, and the need for corrosive additives like acetic acid, which complicates the reaction and increases costs, especially in large-scale industrial applications.
Innovation Solution
A process using a catalyst system comprising specific bidentate diphosphine ligands complexed to iridium or rhodium metals, which operates under elevated pressure in an inert solvent like toluene, achieving high conversion and enantiomeric selectivity without the need for acetic acid or iodide additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If homogeneous iridium-xyliphos catalyst system is used for asymmetric hydrogenation of imines, then enantiomeric selectivity and chemical specificity are improved, but catalyst deactivation occurs and productivity decreases in large batches
Solution Approach 1:
The patent modifies the catalyst system by changing the ligand structure from xyliphos to specifically designed bidentate diphosphine ligands with modified steric and electronic properties. This parameter change in the catalyst structure enables maintaining high enantiomeric selectivity while improving catalyst stability and productivity in large-scale reactions.
Solution Approach 2:
The patent creates a composite catalyst system combining iridium or rhodium metal centers with newly synthesized bidentate diphosphine ligands. This composite approach allows optimization of both catalytic activity and selectivity, resolving the contradiction between manufacturing precision and productivity.
2Productivity
If acetic acid and iodide additive are added to increase catalyst activity, then conversion is improved, but equipment corrosion increases and reaction workup becomes complicated
Solution Approach 1:
The patent extracts and eliminates the need for acetic acid and iodide additives from the reaction system. By designing catalyst systems with inherently higher activity and stability, the patent achieves high conversion without requiring these harmful additives, thus removing the source of corrosion and workup complexity.
Solution Approach 2:
The patent converts the harmful effect of requiring corrosive additives into a benefit by designing catalyst systems that achieve high conversion without them. The new bidentate diphosphine ligands provide sufficient catalytic activity and stability to eliminate the need for acetic acid and iodide, turning a harmful requirement into a non-issue.
3Productivity
If elevated temperature is used to increase reaction rate, then conversion is improved, but catalyst deactivation increases
Solution Approach 1:
The patent changes the catalyst system parameters by introducing bidentate diphosphine ligands with optimized structures that provide thermal stability. This allows the reaction to proceed at elevated temperatures with maintained catalyst activity, resolving the contradiction between reaction rate and stability.
Solution Approach 2:
The patent provides beforehand cushioning against catalyst deactivation by designing catalyst systems with inherent thermal stability. The bidentate diphosphine ligands are structurally designed to resist degradation at elevated temperatures, preventing catalyst deactivation before it can occur.
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 enables high conversion efficiency (>99%) and enantiomeric excess (>76%) of the target amine product, such as S-Metolachlor, while avoiding the use of corrosive additives and maintaining catalyst activity, thus improving economic viability and simplifying the reaction process.
Implementation Method 1
catalytic hydrogenation processes using either homogeneous catalysts or heterogeneous catalysts have played an important role
Implementation Method 2
asymmetric hydrogenation of imines with hydrogen under elevated pressure in the presence of a catalyst system
Data Source
AI summary
The present invention relates to a process for the asymmetric hydrogenation of imines with hydrogen under elevated pressure in the presence of a catalyst system. In particular the present invention relates to the use of the said catalytic system for the enantioselective hydrogenation of prochiral ketimines to asymmetric amines leading to the formation of herbicides.