Silver(I)-Catalyzed Synthesis of β-Oxopropylcarbamates from Propargylic Alcohols and CO2 Surrogate: A Gas-Free Process

Copper-catalyzed four-component reaction of alkenes, Togni's reagent, amines and CO2: stereoselective synthesis of (Z)-enol carbamates

A copper-catalyzed four-component reaction of alkenes, Togni's reagent, amines and CO₂ was disclosed, providing an efficient and straightforward access to a range of stereodefined (Z)-enol carbamates.

Chemical Fixation of CO2 Using Highly Dispersed Cu on Hierarchically Porous N-Doped Carbon

Chemical transformation of carbon dioxide (CO₂) into fine chemicals such as oxazolidinones and carbamates is mainly reported using transition-metal complexes as homogeneous catalysts. Herein, we demonstrate that a heterogeneous catalyst of highly dispersed Cu (Cu/NHPC) supported on hierarchically porous N-doped carbon (NHPC) can efficiently promote CO₂ fixations to oxazolidinones and β-oxopropylcarbamates. The obtained NHPC, assembled by ultrathin nitrogen-doped carbon nanosheets with a three-dimensional (3D) structure, is readily prepared by pyrolysis of a nitrogen-containing polymer gel (NPG) in the presence of an activator of potassium bicarbonate (KHCO₃). The resulting NHPC shows specific Brunauer-Emmet-Teller (BET) surface areas up to 2054 m² g^-1 with a mean micro/mesopore size of 0.55/3.2 nm and a broad macropore size distribution from 50 to 230 nm. The Cu/NHPC can efficiently promote three-component coupling of CO₂, amines, and propargyl alcohols for syntheses of various oxazolidinones and β-oxopropylcarbamates with yields up to 99% and a wide substrate scope. Moreover, the Cu/NHPC exhibits excellent recyclability in CO₂-to-oxazolidinone transformation during nine-time recycling. The research thus develops an NHPC-based heterogeneous Cu catalyst for green transformation of CO₂.

Clever use of natural clay materials in the synthesis of non-symmetric carbonates by utilizing CO2 as a feedstock: Ag/attapulgite nano-catalyst

Using natural minerals seems to be one of the most novel and environmentally friendly strategies to design catalysts for CO₂ conversion. Herein, we report a facile and efficient nano-catalyst for the synthesis of non-symmetric carbonate by utilizing a magnesium-aluminium silicate nano-mineral-attapulgite (ATP). Thanks to the unique structure of ATP and its ability to absorb carbon dioxide, the Ag/attapulgite nano-catalyst has excellent catalytic activity and stability in the carbon dioxide fixation reaction. The design of this Ag/attapulgite nano-catalyst provides a novel idea for realizing CO₂ conversion and clay resource utilization.

CO2 Capture and in situ Catalytic Transformation

The escalating rate of fossil fuel combustion contributes to excessive CO₂ emission and the resulting global climate change has drawn considerable attention. Therefore, tremendous efforts have been devoted to mitigate the CO₂ accumulation in the atmosphere. Carbon capture and storage (CCS) strategy has been regarded as one of the promising options for controlling CO₂ build-up. However, desorption and compression of CO₂ need extra energy input. To circumvent this energy issue, carbon capture and utilization (CCU) strategy has been proposed whereby CO₂ can be captured and in situ activated simultaneously to participate in the subsequent conversion under mild conditions, offering valuable compounds. As an alternative to CCS, the CCU has attracted much concern. Although various absorbents have been developed for the CCU strategy, the direct, in situ chemical conversion of the captured CO₂ into valuable chemicals remains in its infancies compared with the gaseous CO₂ conversion. This review summarizes the recent progress on CO₂ capture and in situ catalytic transformation. The contents are introduced according to the absorbent types, in which different reaction type is involved and the transformation mechanism of the captured CO₂ and the role of the absorbent in the conversion are especially elucidated. We hope this review can shed light on the transformation of the captured CO₂ and arouse broad concern on the CCU strategy.

Catalytic Conversion of Carbon Dioxide through C-N Bond Formation

From the viewpoint of green chemistry and sustainable development, it is of great significance to synthesize chemicals from CO₂ as C₁ source through C-N bond formation. During the past several decade years, many studies on C-N bond formation reaction were involved, and many efforts have been made on the theory. Nevertheless, several great challenges such as thermodynamic limitation, low catalytic efficiency and selectivity, and high pressure etc. are still suffered. Herein, recent advances are highlighted on the development of catalytic methods for chemical fixation of CO₂ to various chemicals through C-N bond formation. Meanwhile, the catalytic systems (metal and metal-free catalysis), strategies and catalytic mechanism are summarized and discussed in detail. Besides, this review also covers some novel synthetic strategies to urethanes based on amines and CO₂. Finally, the regulatory strategies on functionalization of CO₂ for N-methylation/N-formylation of amines with phenylsilane and heterogeneous catalysis N-methylation of amines with CO₂ and H₂ are emphasized.

Fixing CO2 into β-oxopropylcarbamates in neat condition by ionic gelation/Ag(i) supported on dendritic fibrous nanosilica

In this research, a novel approach to produce a novel nanocatalyst, AgBr supported on an ionic gelation (IG)-based nanomaterial, was developed through the aqueous coprecipitation approach for the dendritic fibrous nanosilica (DFNS) production and the wet impregnation method for IG coating, taking into account TPP as the cross-linking agent. In addition, DFNS/IG@Ag(i) had heterogeneous features that contributed to the quick improvement of the catalyst by filtration separation. The catalytic activity of DFNS/IG@Ag(i) was examined to synthesize β-oxopropylcarbamates through a multicomponent coupling of CO₂, amines and propargyl alcohols in moderate conditions. The DFNS/IG@Ag(i) NPs were completely investigated by taking advantage of TG, TEM, FESEM and FT-IR spectroscopy analyses. The DFNS/IG@Ag(i) nanocatalyst indicated high stability in the reaction for five cycles without considerable loss of some properties like activity, which could be because of the high loading of IG on the catalyst surface.

In this research, AgBr supported on an ionic gelation-based nanomaterial, was developed through the aqueous coprecipitation approach for the dendritic fibrous nanosilica (DFNS) production.

Recent advances in nucleophile-triggered CO2-incorporated cyclization leading to heterocycles

CO₂, as a sustainable, feasible, abundant one-carbon synthon, has been utilized in carboxylative cyclization, carbonylative cyclization, and reductive cyclization.

Ureas as safe carbonyl sources for the synthesis of carbamates with deep eutectic solvents (DESs) as efficient and recyclable solvent/catalyst systems

A simple, efficient and eco-friendly one-pot synthesis of primary, N-mono- and N-disubstituted carbamates is developed from ureas.

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.

Silver(I)-Promoted Cascade Reaction of Propargylic Alcohols, Carbon Dioxide, and Vicinal Diols: Thermodynamically Favorable Route to Cyclic Carbonates

A silver(I)-promoted cascade reaction was developed for the synthesis of cyclic carbonates from terminal propargylic alcohols, carbon dioxide, and vicinal diols. Compared with direct condensation of vicinal diols with CO₂, this protocol provides a thermodynamically favorable route to cyclic carbonates and α-hydroxyl ketones in excellent yields (up to 97%) without the additional dehydration step. Such a cascade procedure proceeds presumably through initial reaction of propargylic alcohol with CO₂ and subsequent nucleophilic attack of vicinal alcohol on in situ-formed α-alkylidene cyclic carbonate, resulting in successive generation of α-alkylidene cyclic carbonate, unsymmetrical β-oxoalkyl carbonate, cyclic carbonate, and α-hydroxyl ketone.

Theoretical investigation of boron-doped lithium clusters, BLin (n = 3–6), activating CO2: an example of the carboxylation of C–H bonds

Boron-doped lithium clusters BLin activating CO₂ is reported. And the carboxylation of C–H bond of benzene can be achieved through C–C bond formation and H-atom-transfer from C to O via two H₂O molecules acting as an H-transfer tunnel.