Triethylenediamine CAS 280-57-9 DETA

Since Farben developed the first generation of cast polyurethane elastomers, polyurethane has been widely used due to its unique wear resistance and mechanical properties, and has developed rapidly, with an annual growth rate of more than 4% per year. Among the catalysts for polyurethane foam, the most common and the best performing catalyst is triethylenediamine.

Triethylenediamine has a unique cage-like structure in which two nitrogen atoms are directly linked to three ethylene groups to form a bimolecular structure, which is very dense and symmetrical. Since the N atom not only has no other substituents to increase steric hindrance, but also has a pair of vacant electrons that are very accessible, in the catalytic foaming system, after the urethane bond is formed, triethylenediamine will be freed and participate in next catalytic process. Therefore, although triethylenediamine is not a strong base, it exhibits extremely high catalytic activity towards the reaction of isocyanate groups and active hydrogen compounds.

Taking triethylenediamine catalyzed poly(1,6-hexanediol carbonate) ester diol as an example, firstly, triethylenediamine interacts with 1,6-hexanediol to form hydrogen bonds on the N atom, and increase the The nucleophilicity of the alkoxy group is improved; the nitrogen atom at the other end reacts with dimethyl carbonate to cut off the carbonyl group, and then the elimination reaction is carried out to remove a molecule of methanol, the catalyst is freed for regeneration and continues to catalyze the reaction, and finally the carbon The purpose of chain growth.

In addition to the above application in polyurethane synthesis, another important application of triethylenediamine in organic synthesis is condensation reaction, including Knoevenagel condensation and Ullmann coupling condensation reaction. Triethylenediamine has shown excellent catalytic effect.

1. Knoevenagel condensation: Knoevenagel condensation reaction is a classic reaction of growing carbon chains by forming carbon-carbon double bonds, usually by dehydration of carbonyl compounds (especially aldehydes and ketones) and compounds containing active methylene groups. Classic catalysts are generally acids, bases or . The advantage is that the catalyst is easy to obtain, but the reaction conditions are generally harsh, such as long reaction time, complicated post-processing, etc., so it is difficult to industrially promote or scale up. It has been reported that ionic liquids supported by triethylenediamine or triethylenediamine are currently used as catalysts for Knoevenagel condensation and good results have been achieved. The process is generally divided into two stages. The first is the preparation of ionic liquid catalysts: triethylenediamine reacts with halogen-containing compounds on the N atom to free the halogen, and then reacts with other salts (such as sodium hexafluorophosphate), etc., Improve the performance of the ionic catalyst; secondly, the ionic liquid interacts with aldehydes/ketones to form intermolecular hydrogen bonds to enhance the carbonyl carbonyl positivity. The nitrogen atom at the other end of the ionic liquid captures the active methylene hydrogen atom, and then the two are condensed, and the ionic catalyst is free. and achieve regeneration. Since the two ends of the ionic liquid have dual catalytic activity, the catalytic activity is greatly improved. The mechanism of action is as shown below:

2. Ullmann coupling condensation: Ullmann coupling condensation is the formation of aryl-aryl bonds and aryl-heterocycles

   One of the most important methods of bonding, the commonly used catalysts for this type of reaction are salts of copper, nickel, etc., which generally require a temperature of about 200 °C, and because the catalyst is a solid catalyst with a small catalytic area, the reaction generally takes a long time. to complete. Triethylenediamine was used as a catalyst in Ullmann coupling condensation and it was successful, which provided a new way for the application of Ullmann coupling condensation. Azoxystrobin is a new type of methoxyacrylate fungicide developed by Syngenta. Due to its unique sterilization mechanism, it quickly became the largest-selling fungicide variety after it was launched, and its sales have continued to increase in recent years. The early synthesis process of this product uses potassium carbonate and copper halide as catalysts, and is prepared by high temperature reaction in polar solvent. With this process, not only the reaction time is longer, but the yield is lower. After using triethylenediamine and potassium carbonate as catalysts, the conversion rate is at least over 90%, the reaction yield is over 80%, and the reaction time is shortened to about 70 minutes. However, it was found by comparison that with triethylenediamine and sodium carbonate as catalysts, the yield was significantly reduced and the reaction time was prolonged. It can be seen that the type of base plays a very important role in the catalytic effect of triethylenediamine. In such Ullmann coupling condensation of triethylenediamine, not only the N atom interacts with the corresponding groups participating in the condensation reaction, but also can capture potassium ions through the cage structure, improve the solubility of sodium phenolate, and achieve approximately uniformity. The purpose of the opposite reaction is to shorten the reaction time. The reason for the slow catalytic reaction rate and low yield of sodium carbonate is that the radius of sodium ion is much smaller than that of potassium ion, so triethylenediamine cannot capture sodium ion firmly, and sodium phenolate has low solubility in organic dissolution, and the reaction is still heterogeneous. Instead respond. The reaction process is similar to the following: