Novel and highly efficient transformation of carbon dioxide into 2-oxazolidinones over Al-MCM-41 mesoporous-supported ionic liquids

A type of Al-MCM-41 supported dual imidazolium ionic liquids were constructed and efficiently used as catalysts for the synthesis of 2-oxazolidinones from epoxides, amines, and CO2. The influence of the different catalysts and reaction parameters on the catalytic behaviours was investigated. Al-MCM-41@ILTiCl5 was identified as the most excellent catalyst because it could efficiently promote the three-component cycloaddition of CO2, epoxide, and amines to form the corresponding 2-oxazolidinones in high to excellent yields (84∼96%) with excellent selectivities (98∼99.7%). In addition, the recovery and reuse performances of Al-MCM-41@ILTiCl5 were examined. The catalyst could be recovered by simple filtration and reused six times without a change in the catalytic activity. Green reaction conditions, operational simplicity, feasibility, and sustainability of the functionalized catalyst are the main highlights of the present protocol.

Trimetallic Oxide Foam as an Efficient Catalyst for Fixation of CO2 into Oxazolidinone: An Experimental and Theoretical Approach

The excess anthropogenic CO₂ depletion via the catalytic approach to produce valuable chemicals is an industrially challenging, demanding, and encouraging strategy for CO₂ fixation. Herein, we demonstrate a selective one-pot strategy for CO₂ fixation into "oxazolidinone" by employing stable porous trimetallic oxide foam (PTOF) as a new catalyst. The PTOF catalyst was synthesized by a solution combustion method using transition metals Cu, Co, and Ni and systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), N₂ sorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS) analysis. Due to the distinctive synthesis method and unique combination of metal oxides and their percentage, the PTOF catalyst displayed highly interconnected porous channels along with uniformly distributed active sites on its surface. Well ahead, the PTOF catalyst was screened for the fixation of CO₂ into oxazolidinone. The screened and optimized reaction parameters revealed that the PTOF catalyst showed highly efficient and selective activity with 100% conversion of aniline along with 96% selectivity and yield toward the oxazolidinone product at mild and solvent-free reaction conditions. The superiority of the catalytic performance could be due to the presence of surface active sites and acid-base cooperative synergistic properties of the mixed metal oxides. A doubly synergistic plausible reaction mechanism was proposed for the oxazolidinone synthesis experimentally with the support of DFT calculations along with bond lengths, bond angles, and binding energies. In addition, stepwise intermediate formations with the free energy profile were also proposed. Also, the PTOF catalyst displayed good tolerance toward substituted aromatic amines and terminal epoxides for the fixation of CO₂ into oxazolidinones. Very interestingly, the PTOF catalyst could be significantly reused for up to 15 consecutive cycles with stable activity and retention in physicochemical properties.

Amine-catalyzed site- and stereo-selective coupling of epoxy amines and carbon dioxide to construct oxazolidinones

NEt3 catalyzed the cycloaddition of epoxy amine and CO2, which generated oxazolidinones. Reactions of chiral epoxy amine achieved 100% configuration inversion, enabling the synthesis of linezolid. DFT studies show that NEt3 acted as a nucleophile.

Reaction Mechanism of CO2 and Styrene Oxide Catalyzed by Ionic Liquids: A Combined DFT Calculation and Experimental Study

Bioactive compound 3-aryl-2-oxazolidinone could be synthesized by a green method mixing carbon dioxide, aniline, and ethylene oxide. Our group previously proposed a parallel mechanism for this conversion catalyzed by ionic liquids. Recently, a new study on a similar reaction system of styrene oxide, carbon dioxide, and aniline under the catalysis of K₃PO₄ gave a different serial mechanism. In order to explore the mechanism of reaction, we conducted a combined theoretical and experimental study on a one-pot conversion of styrene oxide, carbon dioxide, and aniline. In experiments, two isomer products, 3,5-diphenyl-l,3-oxazolidin-2-one and 3,4-diphenyl-l,3-oxazolidin-2-one, were observed. The computational results show that the parallel mechanism is more favored in thermodynamics and in kinetics due to the instability of isocyanate and hardness of its generation. Hence, we believe the previous parallel mechanism is more reasonable under our catalysts and conditions.

Synthesis of Benzodiazepines Through Ring Opening/Ring Closure of Benzimidazole Salts

Pyrido-benzodiazepine derivatives are undoubtedly one of the most important structural motifs in the marketed drugs and the drug candidates. Commonly synthetic methods for construction of the benzodiazepine ring derivatives are based on the condensation reactions of two highly functionalized synthons. The development of synthesis for these compounds, however, is hampered by the regioselectivity and atom economy. In this work, a one-step synthesis of pyrido-benzodiazepine backbones and its analogues is achieved through continuous ring-opening hydrolysis of benzimidazole salts and intramolecular C-H bond activation. The reaction mechanism is explored by control experiments and density functional theory (DFT) calculations.

A mild and metal-free synthesis of 2- and 1-alkyl/aryl/dialkyl-aminoquinolines and isoquinolines

A simple synthetic strategy has been developed for the synthesis of 2- and 1-alkyl/aryl/dialkylaminoquinolines and isoquinolines from the easily available quinoline and isoquinoline-N-oxides, different amines, triflic anhydride as activating agent and acetonitrile as solvent in a one-pot reaction under metal-free conditions at 0 °C to room temperature.

Intertwined chemistry of hydroxyl hydrogen-bond donors, epoxides and isocyanates in the organocatalytic synthesis of oxazolidinones versus isocyanurates: rational catalytic investigation and mechanistic understanding

The efficiency and chemoselectivity of the cycloaddition of isocyanates to epoxides to afford oxazolidinones were investigated using hydroxyl hydrogen-bond donors as organocatalysts.

Pyridine-bridged bifunctional organocatalysts for the synthesis of cyclic carbonates from carbon dioxide

Hydroxyl- and carboxyl-functionalized imidazolium halides are used as efficient bifunctional organocatalysts for the synthesis of cyclic carbonates from CO2 and epoxides under mild reaction conditions. Control experiments suggest that the cycloaddition reaction is realized by the combination of the nucleophilic halide anions with hydroxyl and carboxyl groups as hydrogen bond donors. Moreover, the bifunctional organocatalysts can be easily recycled five times by simple filtration; however, a loss of activity was observed.

Advances in the use of CO2 as a renewable feedstock for the synthesis of polymers

Carbon dioxide offers an accessible, cheap and renewable carbon feedstock for synthesis. Current interest in the area of carbon dioxide valorisation aims at new, emerging technologies that are able to provide new opportunities to turn a waste into value. Polymers are among the most widely produced chemicals in the world greatly affecting the quality of life. However, there are growing concerns about the lack of reuse of the majority of the consumer plastics and their after-life disposal resulting in an increasing demand for sustainable alternatives. New monomers and polymers that can address these issues are therefore warranted, and merging polymer synthesis with the recycling of carbon dioxide offers a tangible route to transition towards a circular economy. Here, an overview of the most relevant and recent approaches to CO2-based monomers and polymers are highlighted with particular emphasis on the transformation routes used and their involved manifolds.