Carboxylative Cyclization Of Propargylic Amines Research Articles

Thiadiazol-based conjugated organic polymer anchoring Ag nanoparticles for efficient conversion of CO2 into oxazolidinones from propargylic amines

Efficiently converting CO2 into value-added 2-oxazolidinone under atmospheric pressure remains a great challenging. In this work, a thiadiazole-based conjugated organic polymer (BT-COP) was synthesized for anchoring Ag nanoparticles towards the efficient conversion of CO2 into oxazolidinones from propargylic amines under mild conditions. The S atom in thiadiazole unit acts as an anchoring site for Ag nanoparticles and control their growth. The as-prepared Ag@BT-COP shows a high CO2 adsorption capacity and good catalytic activity and recyclability for the carboxylative cyclization of propargylic amines with CO2 to value-added 2-oxazolidinones under atmospheric pressure. The quasi-in-situ spectroscopy monitoring reaction process and intermediates reveals that the integration of BT-COP and Ag sites into the Ag@BT-COP can serve as a dual catalyst for capturing and activating CO2 and propargylic amines simultaneously.

Carboxylative Cyclization of Propargylic Amines with CO2 Catalyzed by Silver Nanoparticles

Key words silver catalysis - nanoparticles - carbon dioxide - propargylic amines - carboxylative cyclization - oxazolidinones

Palladium-catalyzed carboxylative cyclization of propargylic amines with aryl iodides, CO2 and CO under ambient pressure.

A palladium-catalyzed four-component carboxylative cyclization comprising propargylic amines, aryl iodides, CO2 and CO was developed. By selecting Et3N and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the base, respectively, both terminal and internal propargylic amines proceeded well facilitated by Pd(PPh3)2Cl2, affording the functionalized 2-oxazolones in moderate yields. This protocol enlarges the product diversity based on CO2 conversion and simultaneously provides a cooperative transformation route for both CO2 and CO.

Non-Noble-Metal Metal–Organic-Framework-Catalyzed Carboxylative Cyclization of Propargylic Amines with Atmospheric Carbon Dioxide under Ambient Conditions

The coupling reaction of propargylic amines and carbon dioxide (CO2) to synthesize 2-oxazolidinones is an important reaction in industrial production, and yet harsh reaction conditions and noble-metal catalysts are often required to achieve high product yields. Herein, one novel noble-metal-free three-dimensional framework, [Mg3Cu2I2(IN)4(HCOO)2(DEF)4]n (1), assembled by magnesium and copper clusters was synthesized and applied to this reaction. Compound 1 displays excellent solvent stability. Importantly, 1, acting as heterogeneous catalyst, can highly catalyze the cyclization of propargylic amines with CO2 under atmospheric pressure at room temperature, which can be recycled at least five times without an obvious decrease of the catalytic activity. NMR spectroscopy, coupled with 13C-isotope- and deuterium-labeling experiments, clearly clarifies the mechanism of this catalytic system: CO2 was successfully captured and converted to the product of 2-oxazolidinones, the C≡C bond of propargylic amines can be effectively activated by 1, and proton transfer was involved in the reaction process. Density functional theory calculations are further conducted to uncover the reaction path and the crucial role of compound 1 during the reaction.

Carboxylative Cyclization of a Propargylic Amine with CO2 Catalyzed by a Silica-Coated Magnetite.

By employing a silica-coated magnetite as a catalyst, a silica-catalyzed carboxylative cyclization of propargylic amines with carbon dioxide (CO2) proceeded to afford the corresponding 2-oxazolidinones. Moreover, after the reaction, the silica-coated magnetic catalyst was readily recovered by use of an external magnet and could be reused up to six times without deactivation.

Binuclear Tridentate Hemilabile Copper(I) Catalysts for Utilization of CO2 into Oxazolidinones from Propargylic Amines.

Four binuclear tridentate copper(I) complexes were synthesized based on the trans effect of the hybrid ligands. The catalytic performance and behavior of the prepared copper(I) complexes were evaluated in the carboxylative cyclization of propargylic amines with CO2. The combined use of copper(I) complexes and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) provided a catalytic system for the synthesis of a wide range of oxazolidinones from various propargylic amines and CO2 under mild reaction conditions (room temperature-40 °C and 1 bar CO2). The key factor for the success of the protocol is the use of copper complexes possessing the quality of hemilabile properties between N-heterocyclic carbenes and nitrogen donors. NMR measurements, density functional theory (DFT) calculations, and previous reports for the coordination behavior of the nickel complexes support the existence of the trans effect between N-heterocyclic carbenes and nitrogen donors.

Silica-catalyzed carboxylative cyclization of propargylic amines with CO2

By employing only silica as a catalyst, the carboxylative cyclization of a propargylic amine with CO2 proceeded to afford the corresponding 2-oxazolidinone. MCM-41, which was a mesoporous silica, was found to be the most effective silica for this purpose. Moreover, after the reaction, the MCM-41 catalyst was recovered by filtration and could be reused over ten times without deactivation.

Metal-Free Photocatalytic Synthesis of exo-Iodomethylene 2-Oxazolidinones: An Alternative Strategy for CO2 Valorization with Solar Energy.

A visible-light-promoted metal-free carboxylative cyclization of propargylic amines with CO2 was shown to offer exo-iodomethylene 2-oxazolidinones. Incorporation of both CO2 and iodo moieties into these compounds was realized efficiently. The mechanism study revealed that this carboxylative cyclization proceeds through a radical pathway. Notably, the iodine-functionalized 2-oxazolidinone as a platform molecule could be easily converted into a wide range of value-added chemicals through Buchwald-Hartwig, Suzuki, Sonogashira, photocatalytic ene, and photoreduction reactions. As a result, the plentiful downstream transformations remarkably enhance the range of chemicals derived from CO2 and open a potential avenue for CO2 functionalization to circumvent energy challenges in this field.

Carboxylative Cyclization of Propargylic Amines Catalyzed by Dendrimer-Encapsulated Gold NPs

Key words gold nanoparticles - propargylic amines - carbon dioxide - oxazolidinones - carboxylation - cyclization

Carboxylative Cyclization of Propargylic Amines with Carbon Dioxide­ Catalyzed by Poly(amidoamine)-Dendrimer-Encapsulated Gold Nanoparticles

We prepared gold nanoparticles encapsulated in poly(amidoamine) (PAMAM) dendrimers as templating agents. The resulting gold nanoparticles were used as catalysts for the carboxylative cyclization of propargylic amines with carbon dioxide to afford the corresponding 1,3-oxazolidin-2-ones in yields of up to 99%.

Cobalt-based catalysis for carboxylative cyclization of propargylic amines with CO2 at atmospheric pressure

A cobalt-bicyclic guanidine catalytic system consisting of CoBr2 and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) for the carboxylative cyclization of terminal propargylic amines with CO2 was firstly developed in this work to produce 2-oxazolinones efficiently. The existence of induction period urged us to understand the reaction mechanism of cobalt catalysis. Investigation on the roles of CoBr2 and TBD was conducted using control experiments and density functional theory (DFT) calculation. TBD presumably acts as a base to activate propargylic amine for favorable CO2 capture, and a ligand to coordinate with CoBr2 via forming bulkier CoBr2(TBD) in the same time. This bulkier complex can enhance the O-nucleophility of the in situ formed carbamate intermediate and then promote subsequent intramolecular cyclization to generate 2-oxazolinone, accounting for the high activity of cobalt catalysis. This protocol enables the synthesis of various 2-oxazolinones from propargylic amines and CO2 under atmospheric pressure in good to excellent yields, representing a simple, cost-effective and practical route for CO2 fixation to 2-oxazolinones under mild conditions.

Remarkable synergistic effect between copper(I) and ionic liquids for promoting chemical fixation of CO2

Recently, efficient chemical conversion of CO2 into high value chemicals at room temperature and atmospheric pressure without using noble metal catalysts remains a great challenge. In this work, we find that the carboxylative cyclization of propargylic alcohols with CO2 can proceed at 60°C and ambient pressure by using a combination of CuI and an ionic liquid (IL) 1,8-diazabicyclo-[5.4.0]-7-undecenium trifluoroethanol ([DBUH][TFE]) as catalyst. By simple extraction after the reactions, a series of desired products have been obtained in good to excellent yields with this highly efficient catalyst system. Spectroscopic investigations and DFT calculations demonstrate that such a high efficiency originates from remarkable synergistic catalysis between Cu(I) and the IL on substrates. In addition, it is worth noting that this catalyst system also works well for the carboxylative cyclization of propargylic amines even at ambient temperature and pressure, with the highest turnover number among the reported base metals catalytic systems.

Quaternary ammonium salt-catalyzed carboxylative cyclization of propargylic amines with CO2

By employing quaternary ammonium salts as catalysts, the carboxylative cyclization of the propargylic amines with CO2 proceeded to afford the corresponding 2-oxazolidinones. In particular, tetra-n-butylammonium fluoride was the most effective catalyst for the reaction, providing a 2-oxazolidinone derivative in a maximum chemical yield of 99%. From a screening of the structure of a catalyst, it was found that both a quaternary ammonium cation and a basicity of the counter anion were essential to catalyze the carboxylative cyclization of the propargylic amines with CO2.

An Experimental and Theoretical Study on the Unexpected Catalytic Activity of Triethanolamine for the Carboxylative Cyclization of Propargylic Amines with CO2.

Chemical conversion of CO2 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 propargylic amines with CO2 . Among these alkanolamines, triethanolamine (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 excellent yields. After the reactions, TEOA could be easily recovered and reused without obvious reduction in the efficiency. DFT studies revealed that TEOA may activate CO2 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 production of 2-oxazolidinones.

In Situ Generated Zinc(II) Catalyst for Incorporation of CO2 into 2‐Oxazolidinones with Propargylic Amines at Atmospheric Pressure

Incorporation of CO2 into heterocyclic compounds (i.e., 2-oxazolidinones) under mild conditions, especially at atmospheric pressure still remains challenging. The mononuclear ZnII complex ZnCl2 (TBD)2 , where TBD=1,5,7-triazabicyclo[4.4.0]dec-5-ene, in this study was demonstrated as a robust catalyst for the carboxylative cyclization of propargylic amines with CO2 to exclusively afford various 2-oxazolidinones in excellent yields. Notably, the ZnII catalytic species is readily generated in situ from ZnCl2 and TBD without pre-preparation and further isolation. Such a CO2 fixation protocol could proceed smoothly under atmospheric pressure at mild temperature in an atom economic and environmentally benign manner. 13 C NMR and control experiments were performed to explore the possible interaction between ZnII and the carbon-carbon triple bond of propargylic amine. The dual catalytic role of the Zn catalyst to enhance O-nucleophilicity of the carbamate anion intermediate and activate the carbon-carbon triple bond is proposed based on mechanistic investigations.

ChemInform Abstract: A Carboxylative Cyclization of Propargylic Amines with Carbon Dioxide Catalyzed by the N‐Heterocyclic Carbene 1,3‐Di‐tert‐butylimidazol‐2‐ylidene (ItBu).

AbstractDepending on the pressure of carbon dioxide employed, the carboxylative cyclization of propargylic amines gives selectively 2‐oxazolidiones (III) or 2‐oxazolones (IV).

New Copper(I)/DBU Catalyst System for the Carboxylative Cyclization of Propargylic Amines with Atmospheric CO2: An Experimental and Theoretical Study

Carbon dioxide (CO2) is an abundant and renewable feedstock for the production of high-value chemicals. Herein, CuI and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were employed as an efficient catalyst system to synthesize 2-oxazolidinones through the coupling reaction of CO2 and propargylic amines. It was found that this cost-competitive catalyst system could efficiently catalyze the reaction within only 4 h at atmospheric pressure CO2, and a wide range of substrates were suitable for this reaction. Various target products were obtained in excellent yields. Furthermore, the catalytic mechanism of the CuI/DBU system was investigated by using density functional theory. It was shown that copper(I) and DBU played synergistic roles in activating both the C≡C triple bond and the amino group of propargylic amines in the reaction.

ChemInform Abstract: Robust Silver(I) Catalyst for the Carboxylative Cyclization of Propargylic Alcohols with Carbon Dioxide under Ambient Conditions.

Inspired by the bulkier bis(triphenylphosphine)–silver cation-induced mechanism of propargylic alcohols and carbon dioxide through the alkyl carbonate intermediate, a robust dual-component catalytic system consisting of silver acetate and tetraheptylammonium bromide was rationally developed for the synthesis of α-methylene cyclic carbonates under ambient conditions without employing any additional organic base and ligand. This is one of the most effective catalysts reported to date for this conversion, with a very high turnover number of up to 6024, probably due to the synergistic effect of Lewis basic and Lewis acidic species for the activation of both propargylic alcohol and carbon dioxide by the formation of the alkyl carbonate with a bulkier counterion. Notably, this catalyst also worked well for the carboxylative cyclization of propargylic amines with carbon dioxide with the highest turnover number of 544.

ChemInform Abstract: Carboxylative Cyclization of Propargylic Amines with CO2 Catalyzed by Dendritic N‐Heterocyclic Carbene—Gold(I) Complexes.

AbstractAmphiphilic dentritic NHC‐gold complexes are employed as catalysts for the cyclization of propargyl amines and CO2 to give oxazolidinones under mild reaction conditions.

A Carboxylative Cyclization of Propargylic Amines with Carbon Dioxide Catalyzed by the N‐Heterocyclic Carbene 1,3‐Di‐tert‐butylimidazol‐2‐ylidene (ItBu)

AbstractBy employing N‐heterocyclic carbenes (NHCs) as catalysts, the carboxylative cyclization of propargylic amines proceeded under atmospheric pressure of CO2 (0.1 MPa) to afford the corresponding 2‐oxazolones as the main products. It was considered that the carboxylative cyclization of propargylic amines with CO2 proceeded to initially provide 2‐oxazolidinones, after which the generated 2‐oxazolidinones were consecutively tautomerized to give the corresponding 2‐oxazolones. Moreover, we could perform the NHC‐catalyzed carboxylative cyclization of propargylic amines to provide 2‐oxazolidinones or 2‐oxazolones selectively under controlled reaction conditions.