An Experimental and Theoretical Study on the Unexpected Catalytic Activity of Triethanolamine for the Carboxylative Cyclization of Propargylic Amines with CO 2 Yuling Zhao, [a] Jikuan Qiu, [a] Zhiyong Li, [a] Huiyong Wang, [a] Maohong Fan, [b] and Jianji Wang* [a] Introduction With increasing awareness of growing carbon dioxide levels in the atmosphere, great efforts have been made to develop new strategies and technologies towards the reduction of carbon emissions. [1–3] In fact, CO 2 is usually considered as a ubiquitous, nontoxic, and renewable carbon resource, and can replace commonly used toxic C1 building blocks. [4] Thus, fixation and conversion of CO 2 holds great promise for the recycling of CO 2 into value-added products. At present, many useful organic chemicals that are currently derived from fossil fuel-based re- sources have been produced by using CO 2 as a feed stock, such as alcohols, [5] cyclic carbonates, [6, 7] formamide, [8] and car- boxylic acid derivatives. [9, 10] However, only a small proportion of the total abundance of CO 2 is currently being consumed in industry because to establish ecological and economical CO 2 conversion processes is still a great challenge. Thus the devel- opment of an efficient green process to solve energy and envi- ronmental problems has gained more and more attention re- cently. 2-Oxazolidinones are important heterocyclic compounds that are used as building blocks for different synthetic purpos- es. [11, 12] Synthesis of 2-oxazolidinones from the cycloaddition of propargylic amines with CO 2 has attracted extensive attention in recent years. Many investigations have been conducted for this reaction in the presence of metal catalysts, such as Cu, [13–15] Pa, [16, 17] Ag, [18–23] Ru, [24] and Au. [25–27] It has been demon- strated that these transition metals are good activators for the C C triple bond, thus catalyzing the chemical transformation of substrates with CO 2 . Although CO 2 can be efficiently trans- formed using these catalytic systems, the metal catalysts used in the reactions are both expensive and toxic. Metal-free cata- lytic processes can reduce the cost and avoid the pollution caused by metals, and are thus regarded as a greener process. Over the past decades, a number of metal-free catalysts, such as superbases, [28, 29] N-heterocyclic carbenes, [30] and ionic liquids [13, 31] have been reported to catalyze the carboxylative cyclization of propargylic amines with CO 2 . The most exciting implication is that these catalysts have also shown high activity in comparison with the transition metal catalysts under com- parable reaction conditions. Nevertheless, these reaction sys- tems still have disadvantages, such as the use of high pressure and tedious processes for the preparation of catalysts. There- fore, the development of new organocatalytic systems that can operate under the conditions of low pressure, room tem- perature, and low cost is an urgent task. As a class of low-cost and biodegradable bases, alkanola- mines have been used in a wide variety of industrially impor- tant processes such as natural gas stripping, adhesives, acid neutralization, paint stripping, surfactants, and derivatives in drug formulations. [32–34] As early as 1931, alkanolamines were utilized to capture carbon dioxide from natural gas. [35] This gave us inspiration: maybe alkanolamines can strongly activate CO 2 in the CO 2 conversion process. At present, it is widely rec- ognized that only superbases and their derivatives can serve as single catalysts or can coordinate with metal catalysts to cata- lyze the transformation of CO 2 and propargylic amines. [28, 29, 31] Chemical conversion of CO 2 under atmospheric pressure and metal-free conditions remains a great challenge. In this work, a series of alkanolamines, low-cost and biodegradable bases, were used to catalyze the carboxylative cyclization of propar- gylic amines with CO 2 . Among these alkanolamines, triethanol- amine (TEOA) was found to be a highly efficient organocatalyst for this important transformation at atmospheric pressure, and a series of desired products were synthesized in good to excel- lent yields. After the reactions, TEOA could be easily recovered and reused without obvious reduction in the efficiency. DFT studies revealed that TEOA may activate CO 2 to form a ring- shaped carbonate intermediate that plays an important role in the catalysis of the reaction. This finding provides an effective and environmentally friendly alternative route for the produc- tion of 2-oxazolidinones. [a] Dr. Y. Zhao, J. Qiu, Z. Li, Dr. H. Wang, Prof. Dr. J. Wang Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, School of Chemistry and Chemical Engineering, Key Laboratory of Green Chemical Media and Reactions Ministry of Education, Henan Normal University Xinxiang, Henan 453007 (P. R. China) E-mail : jwang@htu.cn [b] Prof. Dr. M. Fan Department of Chemical and Petroleum Engineering University of Wyoming, Laramie, WY 82071 (USA) Supporting information for this article can be found under: http://dx.doi.org/10.1002/cssc.201700241. ChemSusChem 2017, 10,1–8  2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 & These are not the final page numbers! ÞÞ These are not the final page numbers! ÞÞ Full Papers DOI: 10.1002/cssc.201700241