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A one-pot solvothermal, polyurea (PU) synthesis was reported using propylene carbonate (PC) and methylene-4,4′-dianiline (MDA), organocatalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene. The applied method was performed under auxiliary-free conditions (halogen-, metal-, and co-catalyst-free), avoiding the use of the toxic isocyanates. The synthesized PU served as a macro organocatalyst for the cycloaddition of epichlorohydrin (ECH) and CO2 under the optimized reaction conditions of 130 °C, 24 h and 5 bar CO2, using 0.5 mL dry DMSO and 150 mg catalyst to produce 1.4 g of 4-chloromethyl-2-oxo-1,3-dioxolane. A catalyst reusability study over five consecutive cycles proved the stability of PU, as no decomposition was detected and it could be recovered by simple washing and filtration. After a few cycles, the amine end group of the catalyst was modified by ECH, decreasing the catalytic activity. In addition, density functional theory (DFT) elucidated the cycloaddition mechanism, together with the energetics of the catalytic cycle. It confirmed the accessibility of PU for the epoxide ring activation from both terminal functionalities, with a lower energy barrier for the amine terminated end compared to the alcohol-terminated one. [ABSTRACT FROM AUTHOR]

A multi-active site 1,1′,1′′-(2-hydroxybenzene-1,3,5-triyl)tris(N-benzyl-N,N-dimethylmethanammonium)bromide (3) and hierarchical ionic polymers 9, 11, 13, and 16 have been synthesized. Compound 3 showed the best catalytic activity under co-catalyst free and mild reaction conditions, namely, 1 mL of substrate (epoxide), 2 mol% catalyst loading at 90 °C for 24 h under atmospheric pressure, as compared to its polymeric equivalents (9, 11, 13, and 16). Interestingly, an increase in the number of active sites within the backbone of 3 showed an inverse relationship with the halide nucleophilicity associated with it, viz., Cl− > Br−. This phenomenon arises from the large size of the bromide anion, leading to a 'congested active site' effect, as demonstrated by both experimental and theoretical studies. This was evident as the benzylic ammonium catalyst with bromide ions achieved higher epoxide conversion than its chloride counterpart, whereas the opposite was observed for catalyst 3, likely due to a less congested catalyst structure with chlorides. Unexpectedly, during a five-run recyclability experiment, a modified and less active form of the organocatalyst 3′ was isolated. The overall reaction mechanism was elucidated and further supported by DFT calculations. [ABSTRACT FROM AUTHOR]

Following green chemistry principles, we present a one pot synthesis of zinc curcumin complex as a homogeneous, sustainable catalyst for cyclic carbonate (CC) synthesis from CO2 and a variety of terminal and internal epoxides under 1 bar CO2 at 60 °C using DMSO as a solvent. Zinc curcumin (Zn‐Cur) complex was identified via1H/13C NMR and ATR‐FTIR spectroscopies, elemental analysis, ionic conductivity, and quantitative silver nitrate test to confirm a 1 : 1 molar ratio of metal to the ligand. Interestingly, Zn‐Cur showed an outstanding performance in catalysing the synthesis of renewable CCs including dimeric pinene and limonene carbonates. In this context, other metal complexes, including magnesium (MgII), calcium (CaII), and nickel (NiII) complexes showed good to excellent catalytic activity. Furthermore, a plausible reaction mechanism was investigated by density functional theory (DFT) calculations. The reaction was found to be overall exergonic by 39 kJ/mol and the rate determining step was CO2 insertion, which is in good agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

We reported on sustainable, one-pot synthesized caffeine-based compounds as effective, bifunctional, heterogenous, hydrogen-bond-donor organocatalysts for the cycloaddition of CO2 with several epoxides, supported by a mechanistic study and verified by density functional theory calculations. Two reaction intermediates were isolated during the catalytic cycle: the first involving hydrogen bonding between caffeinium bromide and epichlorohydrin upon exchanging Br− with PF6−, and the second comprising of the nucleophilic attack of Br− followed by ring opening, as deduced from the appearance of a peak corresponding to the C–Br bond in the ATR-FTIR spectrum in the absence of CO2. In this respect, most of the literature is based on postulated mechanisms, racing to achieve lower working conditions, urging us to dig deeper to understand the aforementioned reaction. [ABSTRACT FROM AUTHOR]

CO2 is the most influential greenhouse gas with drastic effects all over the world. Meanwhile, global warming is considered a hot topic to different groups of scientists dealing with the global warming phenomenon. As an alternative to the typically-used scrubbing agent that is heavily used in post-combustion capture technology, namely, monoethanolamine, with its well-known drawbacks, the ionic liquids (ILs) and their corresponding polymers, viz., poly(ionic liquid)s (PILs) have been exploited. In this study, we constructed new imidazolium-based PILs with high surface area fabricated from a 3-(3-(phthalimide)propyl)-1-vinylimidazolium bromide IL-precursor with N-allylphthalimide building blocks, in the presence of divinylbenzene serving as a cross-linker, through a free-radical polymerisation process, and provide their ability for the dual purposes of CO2 capture and utilisation. In this context, the chemical structure of the monomers was fully characterised using elemental analysis, nuclear magnetic resonance and attenuated total reflectance-infrared spectroscopy. The polymeric materials were further examined by thermogravimetric analysis, the Brunauer–Emmett–Teller model and scanning electron microscopy. The sorption characteristics of the amine functionalised PILs were measured volumetrically with CO2 uptake values up to 0.59 mmol CO2 per g sorbent under RTP conditions (25 °C and 1 bar). For CO2 utilisation purposes, the molar ratio of the ionic residues within the polymeric scaffold was increased ranging from one- and two- up to four-fold (×1, ×2, ×4), respectively. Remarkably, the polymeric materials showed excellent catalytic activity for the cycloaddition of CO2 with epoxides to synthesise cyclic carbonates with almost quantitative conversion at 10 bar CO2 and 110 °C. [ABSTRACT FROM AUTHOR]

An in situ generated zinc ascorbate pre-catalyst for cyclic carbonate (CC) synthesis via CO2 coupling with epoxides under ambient conditions was reported. Spectroscopic measurements indicated that CO2 was inserted into the zinc ascorbate complex through the formation of an activated zinc carbonate catalyst upon abstracting the enediol protons with sodium hydride. The aliphatic diols were not activated under the applied conditions and did not interfere with either the process of cycloaddition or CO2 activation. The catalyst was active against different terminal epoxides, with a conversion of 75 and 85%, when propylene oxide and styrene oxide were used at 20 and 50 °C, respectively under 1 atm CO2 for 17 h, which was considered a good advancement for heterogeneous based catalysis. Moreover, green chemistry principles were applied to ultimately end up with more ecofriendly approaches for the synthesis of CC following a simple balloon technique. Herein, we used zinc as a sustainable metal, together with ascorbic acid as a bio-renewable material in addition to CO2 as a renewable feed-stock. Furthermore, waste prevention was achieved using the reaction side product, viz., NaBr as a co-catalyst. [ABSTRACT FROM AUTHOR]

We report on the reaction of ethylene-terminated heteroatoms (C 2 X; X = N, O, and S) with CS 2 /CO 2 using Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) as a promoter for the preparation of imidazolidin-2-one, oxazolidin-2-one, 1,3-dioxolan-2-one, 1,3-dithiolan-2-one, and their thione counterparts at ambient temperature and pressure. Spectroscopic measurements, viz. , 1 H/ 13 C nuclear magnetic resonance (NMR) and ex situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy methods verified the reaction of CS 2 /CO 2 with the ethylene-based substrates and subsequently the formation of cyclic products. The experimental data indicated the formation of the enol -form of imidazolidin-2-one and oxazolidin-2-one, while the keto -form was obtained for their thione correspondents. Furthermore, density functional theory calculations revealed the stability of the keto - over the enol -form for all reactions and pointed out the solvent effect in stabilizing the latter., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)