Acylmethylene Dioxolane Synthesis via Controlled Acid Chloride Acylation
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Solution Overview
Problem
There is a lack of a simple and efficient process for producing acylmethylene-1,3-dioxolanes and acylmethylene-1,4-dioxanes on an industrial scale, as existing methods are prone to spontaneous polymerization and do not provide high yields without interfering side reactions.
Innovation Solution
A process involving the reaction of compounds of formula (II) with acid chlorides or anhydrides, such as methyl oxalyl chloride, in the presence of a base at controlled temperatures, to selectively and efficiently produce acylmethylene-1,3-dioxolanes and acylmethylene-1,4-dioxolanes of formula (I), which are valuable intermediates for pyrazoles and anthranilic acid amides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dioxolane derivatives are reacted with acid anhydrides, then polymerization occurs, but the desired acylmethylene-1,3-dioxolane product is not formed selectively
Solution Approach 1:
The patent changes the reaction parameters by using acid chlorides instead of acid anhydrides, and conducting the reaction at low temperatures (-78°C to 0°C) in the presence of specific bases (triethylamine, pyridine) to prevent polymerization while achieving selective acylation
Solution Approach 2:
The patent introduces a base (triethylamine or pyridine) as an intermediary substance that mediates the reaction between the dioxolane derivative and acid chloride, facilitating the desired acylation while preventing unwanted polymerization side reactions
2Ease of manufacture
If a simple production process is used, then manufacturing complexity is reduced, but spontaneous polymerization occurs
Solution Approach 1:
The patent applies preliminary action by pre-cooling the reaction mixture to low temperatures (-78°C to 0°C) before adding the acid chloride, and by pre-selecting appropriate bases to prevent polymerization before it can occur
Solution Approach 2:
The patent uses periodic action by adding the acid chloride slowly and controlling the reaction temperature throughout the process, maintaining stability while achieving the desired transformation
3Productivity
If existing methods are used to produce acylmethylene-1,3-dioxolanes, then production can occur, but yields are low due to side reactions
Solution Approach 1:
The patent changes multiple reaction parameters simultaneously: using acid chlorides instead of anhydrides, employing specific bases (triethylamine/pyridine), controlling temperature (-78°C to 0°C), and selecting appropriate solvents (dichloromethane, chloroform) to achieve high yields by preventing side reactions
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 selective and high-yield production of acylmethylene-1,3-dioxolanes and acylmethylene-1,4-dioxolanes, avoiding spontaneous polymerization and side reactions, and enables their use as intermediates in the synthesis of insecticidally active compounds, with high purity and suitability for industrial scale-up.
Implementation Method 1
The process according to the invention is characterized in that 4-methylene-1,3-dioxolane and 6-methylene-1,4-dioxane derivatives of the formula (II)... reacts to form acylmethylene-1,3-dioxolanes and acylmethylene-1,4-dioxanes... in the presence of a base
Data Source
AI summary
The invention relates to novel acylmethylene-1,3-dioxolanes and acylmethylene-1,4-dioxanes of the general formula (I), in which R1, R2, R3 and n are defined as in the description, and to a novel method for the production thereof. Acylmethylene-1,3-dioxolanes and acylmethylene-1,4-dioxanes are important intermediate products for producing pyrazoles and anthranilic acid amides, which can be used as insecticides.