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Triethylamine — A Versatile Organocatalyst in Organic Transformations: A Decade Update
Abstract
Organocatalysts play pivotal roles in accomplishing a wide range of useful organic transformations, and organocatalytic reactions are now becoming powerful tools in the construction of simple to complex molecular scaffolds. This remarkable field is growing rapidly with new concepts and designs. During the recent past, triethylamine (or N,N-diethylethanamine), has emerged as an efficient organocatalyst in carrying out so many organic transformations, thereby producing interesting molecular frameworks. Triethylamine is relatively safe, commercially available and cheap. This review offers a decade update on the developments of triethylamine-catalyzed organic transformations reported during the period of 2008 through 2017.
1 Introduction
2 Organocatalytic Applications of Triethylamine in Organic Transformations
2.1 Organic Transformations under Ambient Conditions
2.2 Organic Transformations under Heating/Reflux Conditions
3 Conclusion
... [29][30][31] Over the last decades, Triethylamine (N,N-diethylethanamine) (TEA), which is a water-soluble and colorless liquid, has emerged as an efficient basic catalyst as well as a solvent in various chemical syntheses. [32,33] Moreover, because of its safety, commercially easy availability, and low cost, TEA as a base catalyst has been applied to conduct several synthetic organic reactions some of which are protection of phenols in water, alternative for the Schotten-Baumann method to prepare water-soluble amides, preparation of enantiopure β 2 -amino acids (racemization catalyst) and isoxazole, stereoselective redox cyanation of alk-2-ynals, and much more. [33] However, to the best of our knowledge, there is no report on the synthesis of benzofurans and their derivatives by using TEA as a base. ...
... [32,33] Moreover, because of its safety, commercially easy availability, and low cost, TEA as a base catalyst has been applied to conduct several synthetic organic reactions some of which are protection of phenols in water, alternative for the Schotten-Baumann method to prepare water-soluble amides, preparation of enantiopure β 2 -amino acids (racemization catalyst) and isoxazole, stereoselective redox cyanation of alk-2-ynals, and much more. [33] However, to the best of our knowledge, there is no report on the synthesis of benzofurans and their derivatives by using TEA as a base. As aligned with the context of our studies designed for the optimization of the reaction conditions for the development of convenient and efficient catalytic organic synthesis; [32] herein, we have concentrated on the utility of TEA for the cheap, onepot, and single step straightforward synthesis of benzofuran derivatives under mild conditions. ...
The reaction of substituted salicylaldehydes with α‐haloketones to obtain benzofuran‐2‐yl (Alkyl/aryl) ketones, which is a Dickman type aldol condensation product in base, solvent, and temperature environment, is called as Rap‐Stoermer reaction. In this study, a series of Benzofuran‐2‐yl (Alkyl/ aryl) ketones was synthesized by heating substituted salicylaldehydes and α‐haloketones under solvent‐free sealed (closed vessel) conditions by using triethyleamine (TEA) as a novel base catalyst in good to excellent yields (81–97 %) at 130 °C and the obtained results compared with the existing literature. The reaction conditions were optimized in terms of yield, time, base, solvent temperature, stoichiometric ratios, and synthesis environments (open or closed vessels). The optimized protocol offers promising advantages such as solvent‐free and clean reaction media, short reaction time, no byproducts, and appreciable high yields for the prospective studies. Characterization of the synthesized compounds was performed by using spectroscopic methods such as ATR‐FTIR, 1H‐NMR, 13C‐NMR and LC‐MS.
... However, even at modest levels of exposure, TEA can cause a variety of other health problems when the concentration is too high. It can also cause pulmonary swelling and poisoning when inhaled [107]. TEA is also explosive, and sensitive ZnFe 2 O 4 can be used for its detection. ...
The demand for reliable gas sensing technologies in chemical, manufacturing, environmental, and occupational sites has increased in the last few decades following the global volatile gas sensor market, which is expected to grow further beyond 2025. Currently, several types of sensors have been employed for applications in different fields. Optical sensors are widely implemented in mining and environmental monitoring. Conventional food testing methods are utilized for the detection of any chemical or microbial agent in the food industry. Although robust and sensitive, most sensing technologies are expensive, labor-intensive, and necessitate the use of time-consuming gas sampling pretreatment steps, and these issues impede the achievement of quick, simple detection, portable, and cost-effective gas monitoring. For this reason, researchers around the world are investigating the possibility of using gas sensors as a promising technology that has the potential to alleviate industrial safety concerns. As a highly sensitive semiconducting metal oxide, gas sensors based on ZnFe2O4 have the potential to ensure environmental and occupational safety in real time. This review introduces and highlights recent developments in ZnFe2O4 gas sensors for application in different fields. The challenges limiting the wide application of the ZnFe2O4 sensor are outlined. Furthermore, this review discusses the common strategies adopted to improve the sensing properties of ZnFe2O4 for gas detection. Finally, future perspectives on further improvements of ZnFe2O4 sensing properties are discussed, and integration of ZnFe2O4 sensors into electronic noses to tackle the selectivity issue and how they can feature on the Internet of Things is outlined.
... Triethylamine (TEA) is a colorless volatile organic liquid (VOL) having a fishy smell reminiscent of ammonia. Due to its wide applications as preservatives, solvents, catalysts, and extractants, TEA is often used in industries such as pharmaceuticals, perfumes, pesticides, fuels, anti-hardeners, dyes, and paint removers [1][2][3][4]. TEA vapors are highly toxic within a threshold limit of 10-100 ppm in the air, affecting human health, e.g., causing skin burn, dermatitis, headache, dizziness, somnolence, mucosal, eye lesions, nausea, and even death [2][3][4][5][6]. TEA is also closely related to assessing the freshness of seafood due to its fishy odor, which shows that the increase in TEA concentration would decrease the freshness of fish [7,8]. ...
... Because of its relative safety, commercial availability, and low price, it is often used in industrial production as a synthetic dye and preservative, and because of its excellent physical and chemical properties, it is also used in large quantities in chemical experiments [5]. However, when the TEA concentration is too high, it endangers our physical health by causing injuries such as skin burns and headaches as well as pulmonary edema and poisoning by accidental swallowing; its vapor can also strongly irritate the eyelids and mucous membranes [6,7]. It also has the risk of rapid burning and explosion when exposed to open fire, high temperature, and strong oxidizing agents [8,9]. ...
Triethylamine (TEA) is an organic compound that is commonly used in industries, but its volatile, inflammable, corrosive, and toxic nature leads to explosions and tissue damage. A sensitive, accurate, and in situ monitoring of TEA is of great significance to production safety and human health. Metal oxide semiconductors (MOSs) are widely used as gas sensors for volatile organic compounds due to their high bandgap and unique microstructure. This review aims to provide insights into the further development of MOSs by generalizing existing MOSs for TEA detection and measures to improve their sensing performance. This review starts by proposing the basic gas-sensing characteristics of the sensor and two typical TEA sensing mechanisms. Then, recent developments to improve the sensing performance of TEA sensors are summarized from different aspects, such as the optimization of material morphology, the incorporation of other materials (metal elements, conducting polymers, etc.), the development of new materials (graphene, TMDs, etc.), the application of advanced fabrication devices, and the introduction of external stimulation. Finally, this review concludes with prospects for using the aforementioned methods in the fabrication of high-performance TEA gas sensors, as well as highlighting the significance and research challenges in this emerging field.
With outstanding AIE effect, TPE-substituted chalcone derivatives were widely used in the field of mechanochromic luminescent materials, chemical sensors, biosensing, etc. However, TPE-substituted chalcones which could function as pH indicator have not yet been reported until now. In this paper, three novel TPE-substituted chalcones were designed and synthesized as pH indicator for the first time. These TPE-substituted chalcones exhibited sensitive pH-chromic properties with continuous end points (pH = 9.77, 10.98 and 11.51 respectively). These pH indicators can be employed in fabrication of pH strips with higher accuracy compared to universal pH strips. Detection of Et3N can also be realized by these TPE-substituted chalcones with advantages in low cost, high sensitivity, easy-handle and real-time.
In this work, platinum-loaded In2O3 (Pt/In2O3) nanosheets were synthesized and their triethylamine (TEA) sensing performance was improved by hydrogen treatment. The response of 0.25 Pt/In2O3 (H2) to 100 ppm TEA was as high as 4792, which was 12 times the untreated one. The detection limit of 0.25 Pt/In2O3 (H2) was 50 ppt. The samples before and after hydrogen treatment were analyzed by various techniques. It was found that the supported Pt had a high degree of dispersion. Even after hydrogen treatment, most Pt in the 0.25 Pt/In2O3 (H2) existed in the form of single atoms. Pt loading and hydrogen treatment can improve the electron mobility of In2O3. Besides, after hydrogen treatment, the number of low-valence Pt increased, which promoted the generation of adsorbed oxygen and reduced the TEA response energy barrier, thereby enhancing the sensitivity to TEA. These findings are significant for the design of supported metal sensing materials and show the importance of hydrogen treatment in improving the response of Pt-loaded sensing materials and the crucial role of low-valence Pt in TEA sensing performance.
Background
Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been using to accelerate organic transformations. With the development of environmental awareness, in order to obtain highly privileged scaffolds, scientists have directed their studies towards the synthetic methodologies which minimize or preferably eliminate the formation of waste, avoid from toxic solvents and reagents and use renewable starting materials as far as possible.
Methods
In this connection, the organocatalytic reactions providing efficiency and selectivity for most of case have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts supplying transformation of reactants into products with the least possible waste production have been serving to the concept of green chemistry.
Results and Conclusion
Organocatalysts have been classified on the basis of their binding capacity to the substrate with covalently or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.
This study presents a nontarget approach to detect discharges from pharmaceutical production in municipal wastewater treatment plant (WWTP) effluents and to estimate their relevance on the total emissions. Daily composite samples were collected for 3 months at two WWTPs in Switzerland, measured using liquid chromatography high-resolution mass spectrometry, and time series were generated for all features detected. The extent of intensity variation in the time series was used to differentiate relatively constant domestic inputs from highly fluctuating industrial emissions. We show that an intensity variation threshold of 10 correctly classifies compounds of known origin and reveals clear differences between the two WWTPs. At the WWTP receiving wastewater from a pharmaceutical manufacturing site, (i) 10 times as many potential industrial emissions were detected as compared to the WWTP receiving purely domestic wastewater; (ii) for 11 pharmaceuticals peak concentrations, >10 μg/L and up to 214 μg/L were quantified, which are clearly above typical municipal wastewater concentrations; and (iii) a pharmaceutical not authorized in Switzerland was identified. Signatures of potential industrial emissions were even traceable at the downstream Rhine monitoring station at a >4000-fold dilution. Several of them occurred repeatedly, suggesting that they were linked to regular production, not to accidents. Our results demonstrate that small wastewater volumes from a single industry not only left a clear signature in the effluents of the respective WWTP but also influenced the water quality of one of Europe's most important river systems. Overall, these findings indicate that pharmaceutical production is a relevant emission source even in highly developed countries with a strong focus on water quality, such as Switzerland.
A systematized survey of reviews and monographs published in 2018 on all aspects of heterocyclic chemistry is given.
Triethylamine is a volatile organic compound and harmful to the environment. Development of an efficient detection and conversion method for triethylamine becomes urgent. In this work, Pt loaded three-dimensionally ordered macroporous (3DOM) WO3 materials were successfully synthesized through a colloidal crystal template method. Compared to Pt clusters on the surface, atomically dispersed Pt (II) on WO3 increased the number of active sites and decrease the activation energy, which resulted in highly efficient oxidation and high sensitivity detection of triethylamine. The sensor based on the 3DOM SA-Pt/WO3 with atomically dispersed Pt (II) exhibited super high sensitivity (28.37 ppm⁻¹) and ultra-low detection limit (0.18 ppb) to triethylamine. The high selectivity possibly originated from the selective adsorption of triethylamine from other volatile organic compounds on the uniform single atom Pt (II) sites.