2-Haloacrylic Ester Synthesis via Base-Promoted Decarboxylation
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Solution Overview
Problem
Existing processes for preparing 2-haloacrylic esters, such as 2-fluoroacrylic esters, suffer from low yields and are economically and safety-wise unsuitable for industrial applications due to the need for multiple stages and hazardous reactants.
Innovation Solution
A process involving the reaction of compounds of the formula (II) or (III) with a base to eliminate carbon dioxide and a halide, bypassing the formation of free 2-haloacrylic acid, thereby simplifying the process and increasing yield and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple process stages are used to prepare 2-haloacrylic esters (hydrolysis, decarboxylation, reesterification), then the reaction can proceed through known pathways, but the yield is low and the process is economically unviable
Solution Approach 1:
The patent combines multiple reaction steps (decarboxylation and elimination) into a single concerted reaction step. The malonic diester undergoes base-promoted decarboxylation and simultaneous elimination of the hydroxymethyl or halomethyl group to directly form the 2-haloacrylic ester, eliminating the need for separate hydrolysis, decarboxylation, and reesterification steps while achieving high yields
Solution Approach 2:
The reaction is segmented into a direct one-step transformation from malonic diester to 2-haloacrylic ester by using a base promoter that facilitates both decarboxylation and elimination simultaneously, avoiding the need to isolate hazardous intermediates like free 2-haloacrylic acid
2Reliability
If hazardous intermediates like free 2-haloacrylic acid are formed, then the reaction pathway follows known chemistry, but safety risks increase and economic viability decreases
Solution Approach 1:
The reaction conditions are designed to promote concerted decarboxylation and elimination in a single step, preventing the formation of free 2-haloacrylic acid intermediate. The base promoter facilitates the simultaneous occurrence of both reactions, so the hazardous intermediate is never generated
Solution Approach 2:
A base promoter (such as alkali metal hydroxides, carbonates, or alkoxides) acts as an intermediary that facilitates the concerted reaction mechanism. The base promotes both decarboxylation and elimination simultaneously, providing a safe pathway that avoids hazardous intermediates while maintaining reaction efficiency
3Reliability
If reactants like 2,2-bromofluoropropionic esters are used, then substitution reactions can proceed, but the reactants are barely available and yields are low
Solution Approach 1:
Instead of using rare and expensive reactants like 2,2-bromofluoropropionic esters that require substitution reactions, the patent inverts the approach by using readily available malonic diesters as starting materials. The base-promoted decarboxylation-elimination pathway converts common malonic diesters directly into 2-haloacrylic esters, improving both reactant availability and yield
4Reliability
If four-stage processes are used to prepare 2-fluoroacrylic esters from 2,3-dichloro-1-propene, then the reaction can proceed through known steps, but the process becomes economically and safety-wise undesirable
Solution Approach 1:
The patent merges four separate process stages into a single reaction step. The base-promoted concerted decarboxylation-elimination of malonic diesters achieves in one step what previously required four stages, thereby simplifying the process while maintaining complete transformation and high yield
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 allows for the preparation of 2-haloacrylic esters in high yields and purity, eliminating the need for hazardous intermediates and reducing the number of process stages, making it suitable for industrial-scale production of plastics and polymeric additives.
Implementation Method 1
reacting compounds of the formula (II) and/or compounds of the formula (III) in each of which R1 and X1 have the definition given for formula (IV) and the two R1 radicals are identical or different, preferably identical, and where X2 in formula (III) is fluorine, chlorine, chlorosulfinyloxy or bromine, in the presence of base to give compounds of the formula (IV)
Data Source
AI summary
The present invention relates to a process for preparing 2-haloacrylic esters from 2-hydroxymethyl- or 2-halomethyl- or 2-chlorosulfinyloxymethyl-2-halomalonic diesters. The invention further provides novel 2-halomethyl-2-halomalonic diesters or 2-chlorosulfinyloxymethyl-2-halomalonic diesters which can be used for preparation of the 2-haloacrylic esters.