Continuous Synthesis of Carbamates from CO2 and Amines

We present a novel approach for the continuous preparation of carbamates. The simple yet fast synthetic route relies on directly utilizing carbon dioxide and, in contrast with the literature-known methods, only employs 1,8-diazabicyclo[5.4.0]undec-7-ene as an additive. The applicable amines' diversity offers considerable flexibility to the synthetic protocol. Additionally, the continuous method's applicability significantly decreases the reaction time typically required for CO2-based carbamate synthesis and allows for straightforward and precise gas introduction. The mild reaction conditions and omission of the need for column chromatography render the process less time-demanding and environmentally more benign, providing the desired compounds in yields of 45 to 92%. Moreover, the modified procedure can potentially be applied in the selective synthesis of oxazolidinones from aziridines.

Bimetallic Metal-Organic Framework Derived Nanocatalyst for CO2 Fixation through Benzimidazole Formation and Methanation of CO2

In this paper, a bimetallic Metal-Organic Framework (MOF) CoNiBTC was employed as a precursor for the fabrication of bimetallic nanoalloys CoNi@C evenly disseminated in carbon shells. These functional nanomaterials are characterized by powdered X-ray diffraction (PXRD), Fourier Transform Infra-Red spectroscopy (FTIR), surface area porosity analyzer, X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Hydrogen Temperature-Programmed Reduction (H2 TPR), CO2 Temperature-Programmed Desorption (CO2-TPD), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This nanocatalyst was utilized in the synthesis of benzimidazole from o-phenylenediamine in the presence of CO2 and H2 in a good yield of 81%. The catalyst was also efficient in the manufacture of several substituted benzimidazoles with high yield. Due to the existence of a bimetallic nanoalloy of Co and Ni, this catalyst was also employed in the methanation of CO2 with high selectivity (99.7%).

Constructing a metal-free 2D covalent organic framework for visible-light-driven photocatalytic reduction of CO2: a sustainable strategy for atmospheric CO2 utilization

A 2D polyimide-linked covalent organic framework (COF) with band gap energy of 2.2 eV is developed as a stable and efficient porous photocatalyst which shows CO2 reduction to formic acid, formaldehyde and methanol.

Supported Metal Catalysts for the Synthesis of N-Heterocycles

Nitrogen-containing heterocycles are important scaffolds for a large number of compounds with biological, pharmaceutical, industrial and optoelectronic applications. A wide range of different methodologies for the preparation of N-heterocycles are based on metal-catalyzed cyclization of suitable substrates. Due to the growing interest in Green Chemistry criteria over the past two decades, the use of supported metal catalysts in the preparation of N-heterocycles has become a central topic in Organic Chemistry. Here we will give a critical overview of all the solid supported metal catalysts applied in the synthesis of N-heterocycles, following a systematic approach as a function of the type of support: (i) metal catalysts supported on inorganic matrices; (ii) metal catalysts supported on organic matrices; (iii) metal catalysts supported on hybrid inorganic-organic matrices. In particular, we will try to emphasize the effective heterogeneity and recyclability of the described metal catalysts, specifying which studies were carried out in order to evaluate these aspects.

Zn(II)-Functionalized COF as a Recyclable Catalyst for the Sustainable Synthesis of Cyclic Carbonates and Cyclic Carbamates from Atmospheric CO2

A simple covalent organic framework (COF) bearing β-ketoenamine units as a potential heterogeneous ligand for ZnII-catalyzed fixation and transformation of CO2 into value-added chemicals is reported. Catalytic investigations convincingly demonstrated...

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.

Recent advancements on Benzimidazole: A versatile scaffold in medicinal chemistry

Benzimidazole is nitrogen containing fused heterocycle which has been extensively explored in medicinal chemistry. Benzimidizole nucleus has been found to possess various biological activities such as anticancer, antimicrobial, anti-inflammatory, antiviral, antitubercular and antidiabetic. A number of benzimidazoles such as bendamustine, pantoprazole have been approved for the treatment of various illnesses whereas galeterone and GSK461364 are in clinical trials. The present review article gives an overview about the different biological activities exhibited by the benzimidazole derivatives as well as different methods used for the synthesis of benzimidazole derivatives for the past ten years.

Triazine-based Organic Polymer-catalysed Conversion of Epoxide to Cyclic Carbonate under Ambient CO2 Pressure

In this work we have achieved epoxide to cyclic carbonate conversion using a metal-free polymeric catalyst under ambient CO₂ pressure (1.02 atm) using a balloon setup. The triazine containing polymer (CYA-ANIS) was prepared from cyanuric chloride (CYA-Cl) and o-dianisidine (ANIS) in anhydrous DMF as solvent by refluxing under the N₂ gas environment. The presence of triazine and amine functional groups in the polymer results in the adsorption of CO₂ up to 7 cc/g at 273 K. This inspired us to utilize the polymer for the conversion of a series of functionalised epoxides into their corresponding cyclic carbonates in the presence of tetrabutyl ammonium iodide (TBAI) as co-catalyst. The product has wide range of applications like solvent in lithium ion battery, precursor for polycarbonate, etc. The catalyst was efficient for the conversion of different mono and di-epoxides into their corresponding cyclic carbonates under atmospheric pressure in the presence of TBAI as co-catalyst. The study indicates that epoxide attached with electron withdrawing groups (like, CH₂ Cl, glycidyl ether, etc.) displayed better conversion compared to simple alkane chain attached epoxides. This is mainly due to the stabilization of electron rich intermediates produced during the reaction (e. g. epoxide ring opening or CO₂ incorporation into the halo-alkoxide anion). This catalyst mixture was capable to maintain its reactivity up to five cycles without losing its activity. Post catalytic characterization clearly supports the heterogeneous and recyclable nature of the catalyst.

Heterogeneous catalysis for the tandem cyclisation of unsaturated alcohols

A methodology for the tandem cycloisomerisation of doubly unsaturated alcohols using Amberlyst-15 was developed.

DNA intercalative trinuclear Cu(ii) complex with new trans axial nitrato ligation as an efficient catalyst for atmospheric CO2 fixation to epoxides

A trinuclear octahedral Cu^II complex was synthesized and structurally characterized by single crystal X-ray diffraction studies and behaved as a catalyst for CO₂ fixation to epoxide and as a DNA binder.

An efficient one-pot synthesis of industrially valuable primary organic carbamates and N-substituted ureas by a reusable Merrifield anchored iron(ii)-anthra catalyst [FeII(Anthra-Merf)] using urea as a sustainable carbonylation source

A Merrifield anchored iron(ii)-anthra catalyst [FeII(Anthra-Merf)] has been synthesized for the production of primary carbamates and N-substituted ureas using a carbonylation source.

Triazinetriamine-derived porous organic polymer-supported copper nanoparticles (Cu-NPs@TzTa-POP): an efficient catalyst for the synthesis of N-methylated products via CO2 fixation and primary carbamates from alcohols and urea

Copper nanoparticles incorporated triazinetriamine derived porous organic polymer based catalyst was synthesized for catalytic production N-methylated amines and primary carbamates.

Synthesis of benzimidazolones via CO2 fixation and N-phenyl formamides using formic acid in presence of zinc embedded polymer complex

A merrifield supported heterogeneous zinc catalyst [Zn(Meri-Ald-Py)] was synthesized and applied for benzimidazolone synthesis through the fixation of carbon dioxide (CO₂) and for different N-formylated products synthesis under mild reaction conditions.