Rhodium-Catalyzed Isomerization for Beta-Functionalized Esters
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Solution Overview
Problem
Current methods for isomerizing functionalizations of long-chain unsaturated fatty esters are limited, with most reactions occurring at the methyl terminus of the alkyl chain, and there is a need for more efficient one-pot reaction sequences to produce β-functionalized aliphatic esters.
Innovation Solution
A rhodium-catalyzed one-pot method involving the isomerization of unsaturated esters with a boron compound or amine in the presence of a rhodium catalyst under an oxygen-free atmosphere at elevated temperatures, allowing for the selective formation of β-functionalized carboxylic acid esters by depleting and replenishing reversible double bond isomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional isomerization reactions are used on long-chain unsaturated fatty esters, then reactions occur at the methyl terminus of the alkyl chain, but this limits access to internal positions for functionalization
Solution Approach 1:
The patent changes the reaction parameters by introducing a rhodium catalyst with specific ligands (Biphephos or P(Oallyl)3) and adjusting temperature (80-120°C) to shift the isomerization equilibrium toward internal double bonds, enabling functionalization at positions other than the methyl terminus
Solution Approach 2:
The rhodium catalyst acts as an intermediary that facilitates controlled isomerization of the double bond position, allowing the substrate to transform from a non-functionalizable state to a functionalizable state at internal positions
2Manufacturing precision
If multiple separate reaction steps are used to achieve β-functionalized esters, then functionalization can be achieved, but the process becomes costly and time-consuming
Solution Approach 1:
The patent merges two separate reactions (isomerization and conjugate addition) into a single one-pot reaction sequence, where the rhodium catalyst first isomerizes the double bond to the internal position, then the nucleophile adds in a conjugate fashion, achieving β-functionalized esters without requiring separate reaction steps
Solution Approach 2:
The isomerization step is performed preliminarily within the same reaction pot before the conjugate addition occurs, preparing the substrate in the correct configuration for subsequent functionalization without requiring isolation or separate processing
3Productivity
If oxygen is present during the reaction, then the reaction can proceed, but oxidation side reactions occur reducing yield and product quality
Solution Approach 1:
The patent employs an inert atmosphere (nitrogen or argon) throughout the reaction process to exclude oxygen, preventing oxidation side reactions while maintaining the reaction rate through controlled thermal conditions (80-120°C) and catalytic activation
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 enables the efficient production of β-functionalized esters with high yields, as demonstrated by specific examples, and can be applied to fatty esters derived from renewable sources, offering potential applications in cosmetics and UV filters.
Implementation Method 1
a rhodium containing catalyst selected as defined in claim 1
Implementation Method 2
Based on the principle of the thermodynamic equilibrium of isomers, the method according to the present application is a catalytic one-pot method that allows the access of remote double bonds in olefinic esters for the reaction with nucleophiles into β-functionalized compounds. From a rapidly inter-converting pool of positional double bond isomers, only the α,β-unsaturated species is depleted by the conjugate addition reaction, and it is replenished by the other isomers with which it is in reversible equilibrium.
Implementation Method 3
a rhodium-catalyzed double bond isomerization/conjugate addition will provide a valuable new approach to prepare ß-functionalized esters
Implementation Method 4
reacting in one-pot an unsaturated ester according to general formula (II) in the presence of either an a boron compound selected as defined in claim 1 or an amine R'''-NH-R'''' (IV), whereby R''' and R'''' have the same meaning as above and a rhodium containing catalyst selected as defined in claim 1
Implementation Method 5
under an oxygen-free atmosphere at temperatures between 80 - 120 °C in a solvent
Data Source
AI summary
The invention pertains to a new route to prepare ß-functionalized carboxylic acid esters in a one-pot reaction, by reacting an olefinic acid ester in the presence of a catalyst system, comprising a Rh(I)-complex, together with an aryl boron or a diamine as nucleophilic compounds, and under oxygen-free conditions and elevated temperatures.