A Chitosan Derivative Containing Both Carboxylic Acid and Quaternary Ammonium Moieties for the Synthesis of Cyclic Carbonates

State-of-the-art phosphorylation of water-soluble allyl cellulose via a green radical-mediated "click" reaction pathway with enhanced antifungal activity

Allyl Cellulose (AC) was synthesized using allyl bromide in sodium hydroxide (NaOH)/urea aqueous solution. By employing a molar ratio of 6:1 of allyl bromide/cellulose, low-degree of substitution (DS) water-soluble AC (AC1) was obtained (DS = 0.67). Then, radical-mediated "click" reactions of AC1 with diethyl phosphite (DEP) and dibutyl phosphite (DBP) were carried out in deionized water as green reaction medium, using 4,4'-azobis(4-cyanovaleric acid) (ACVA) as a radical initiator. The synthesized AC1-DEP and AC1-DBP showed high conversion percentages of 84 % and 87 %, respectively. Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) techniques were used to validate the structure of the products and confirm the successful radical-mediated "click" reactions of AC1 with dialkyl phosphite (DAP) in water. X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), static contact angle, and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) analyses were used to investigate structural, thermal, and surface properties, revealing an increase in flexibility and hydrophobicity upon phosphorylation. AC1-diethyl phosphite (AC1-DEP) and AC1-dibutyl phosphite (AC1-DBP) exhibited efficient antifungal activities with inhibition zone ranges from 14 to 27 mm.

Engineering chitosan into fully bio-sourced, water-soluble and enhanced antibacterial poly(aprotic/protic ionic liquid)s packaging membrane

The design and facile preparation of water-soluble and eco-friendly polymer packaging membrane materials is a fascinating research topic, particularly in terms of the increasing concerns on potential microplastics pollution in ecosystem. In this study, taking advantages of the structural features of chitosan (CS) and betaine hydrochloride (BHC), fully bio-sourced and water-soluble poly(aprotic/protic ionic liquid)s (PAPILs) were successfully designed and prepared through the reaction of the amino groups in CS and carboxyl groups in BHC. The structure and thermo-properties of the PAPILs were elucidated by a series of characteristic methods. The rheological properties of the PAPILs aqueous solutions were also investigated. Moreover, water-soluble PAPILs membrane with a smooth surface morphology and a tensile strength of 62.9 MPa was successfully prepared. The PAPILs membrane also exhibited satisfactory biocompatibility, excellent antibacterial activities and high oxygen barrier property. Together with these outstanding material performance and functionality, as a "proof of concept", the potential use of the PAPILs membrane as water-soluble packaging material for laundry detergent capsule and pesticide was preliminarily demonstrated. These findings provide significant insights for the design of sustainable and functional packaging materials by using natural resources.

Alumina-Based Bifunctional Catalyst for Efficient CO2 Fixation into Epoxides at Atmospheric Pressure

The quest toward sustainability and decarbonization demands the development of methods for efficient carbon dioxide capture and utilization. The nonreductive CO₂ fixation into epoxides to prepare cyclic carbonates has gained attention in recent years. In this work, we report the development of guanidine hydrochloride-functionalized γ alumina (γ-Al₂O₃), prepared using green solvents, as an efficient bifunctional catalyst for CO₂ fixation. The resulting guanidine-grafted γ-Al₂O₃ (Al-Gh) proved to be an excellent catalyst to prepare cyclic carbonates from epoxides and CO₂ with high selectivity. The nitrogen-rich Al-Gh shows increased CO₂ adsorption capacity compared to that of γ-Al₂O₃. The as-prepared catalyst was able to carry out CO₂ fixation at 85 °C under atmospheric pressure in the absence of solvents and external additives (e.g., TBAI or KI). The material showed negligible loss of catalytic activity even after five cycles of catalysis. The catalyst successfully converted many epoxides into their respective cyclic carbonates under the optimized conditions. The gram-scale synthesis of commercially important styrene carbonates from styrene oxide and CO₂ using Al-Gh was also achieved. Density functional theory (DFT) calculations revealed the role of alumina in activating the epoxide. This activation facilitated the chloride ion to open the ring to react with CO₂. The DFT studies also validated the role of alumina in stabilizing the electron-rich intermediates during the course of the reaction.

A comprehensive survey upon diverse and prolific applications of chitosan-based catalytic systems in one-pot multi-component synthesis of heterocyclic rings

Heterocyclic compounds are among the most prestigious and valuable chemical molecules with diverse and magnificent applications in various sciences. Due to the remarkable and numerous properties of the heterocyclic frameworks, the development of efficient and convenient synthetic methods for the preparation of such outstanding compounds is of great importance. Undoubtedly, catalysis has a conspicuous role in modern chemical synthesis and green chemistry. Therefore, when designing a chemical reaction, choosing and or preparing powerful and environmentally benign simple catalysts or complicated catalytic systems for an acceleration of the chemical reaction is a pivotal part of work for synthetic chemists. Chitosan, as a biocompatible and biodegradable pseudo-natural polysaccharide is one of the excellent choices for the preparation of suitable catalytic systems due to its unique properties. In this review paper, every effort has been made to cover all research articles in the field of one-pot synthesis of heterocyclic frameworks in the presence of chitosan-based catalytic systems, which were published roughly by the first quarter of 2020. It is hoped that this review paper can be a little help to synthetic scientists, methodologists, and catalyst designers, both on the laboratory and industrial scales.

The Application of Biomass-Based Catalytic Materials in the Synthesis of Cyclic Carbonates from CO2 and Epoxides

The synthesis of cyclic carbonates from carbon dioxide (CO2) and epoxides is a 100% atom economical reaction and an attractive pathway for CO2 utilisation. Because CO2 is a thermodynamically stable molecule, the use of catalysts is mandatory in reducing the activation energy of the CO2 conversion. Considering environmental compatibility and the high-efficiency catalytic conversion of CO2, there is the strong need to develop green catalysts. Biomass-based catalysts, a type of renewable resource, have attracted considerable attention due to their unique properties-non-toxic, low-cost, pollution-free, etc. In this review, recent advances in the development of biomass-based catalysts for the synthesis of cyclic carbonates by CO2 and epoxides coupling are summarized and discussed in detail. The effect of biomass-based catalysts, functional groups, reaction conditions, and co-catalysts on the catalytic efficiency and selectivity of synthesizing cyclic carbonates process is discussed. We intend to provide a comprehensive understanding of recent experimental and theoretical progress of CO2 and epoxides coupling reaction and pave the way for both CO2 conversion and biomass unitization.

Cycloaddition of carbon dioxide to epoxides catalysed by supported ionic liquids

Simple hybrid silica-imidazolium based ILs as highly active and selective catalysts for the carbonation of epoxides in batch and continuous flow systems under mild reaction conditions.

Recyclable Single-Component Rare-Earth Metal Catalysts for Cycloaddition of CO2 and Epoxides at Atmospheric Pressure

Ionic rare-earth metal complexes 1-4 bearing an imidazolium cation were synthesized, which, as single-component catalysts, showed good activity in catalyzing cyclic carbonate synthesis from epoxides and CO₂. In the presence of 0.2 mol % catalyst, monosubstituted epoxides bearing different functional groups were converted into cyclic carbonates in 60-97% yields under atmospheric pressure. In addition, bulky/internal epoxides with low reactivity yielded cyclic carbonates in 40-95% yields. More importantly, the readily available samarium complex 2 was reused for six successive cycles without any significant loss in its catalytic activity. This is the first recyclable rare-earth metal-based catalyst in cyclic carbonate synthesis.

Inclusion complexes of organic salts with β-cyclodextrin as organocatalysts for CO2 cycloaddition with epoxides

The inclusion complexes between β-cyclodextrin and 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU)-based phenolates have been developed and employed as heterogeneous catalysts for the cycloaddition of CO₂ to cyclic carbonate.

Organocatalyzed coupling of carbon dioxide with epoxides for the synthesis of cyclic carbonates: catalyst design and mechanistic studies

The coupling of carbon dioxide (CO₂) with epoxides with the formation of cyclic carbonates is a highly attractive 100% atom economic reaction. It represents a greener and safer alternative to the conventional synthesis of cyclic carbonates from diols and toxic phosgene.