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.

Discovery of new benzhydrol biscarbonate esters as potent and selective apoptosis inducers of human melanomas bearing the activated ERK pathway: SAR studies on an ERK MAPK signaling modulator, ACA-28.

The recent discovery that an ERK signaling modulator [ACA-28 (2a)] preferentially kills human melanoma cell lines by inducing ERK-dependent apoptosis has generated significant interest in the field of anti-cancer therapy. In the first SAR study on 2a, here, we successfully developed candidates (2b, 2c) both of which induce more potent and selective apoptosis towards ERK-active melanoma cells than 2a, thus revealing the structural basis for inducing the ERK-dependent apoptosis and proposing the therapeutic prospect of these candidates against ERK-dependent cancers represented by melanoma.

Synthesis and Antibacterial Activity of New N-Alkylammonium and Carbonate-Triazole Derivatives within Desosamine of 14- and 15-Membered Lactone Macrolides.

Desosamines of azithromycin (AZM) and clarithromycin (CLA) were modified by N-alkylation or nucleophilic substitution at the carbonyl/CuAAC sequence. Biological studies revealed a higher antibacterial potency of quaternary N-alkylammonium bromides of CLA as compared to AZM. SAR studies of CLA salts, including biological, conformation and molecular-docking analysis, enriched by physicochemical parameters, showed the importance of less bulky and unsaturated substituent for an efficient docking mode at the ribosomal tunnel and good antibacterial potency against clinical and standard Streptococcus pneumoniae and Streptococcus pyogenes strains (MICs 0.25 or 0.5 µg/mL). These CLA salts also have an at least threefold lower cytotoxicity than reference antibiotics at comparable antibacterial activity against the S. pneumoniae clinical strain. Differences in antibacterial effects noted for AZM and CLA salts bearing less bulky N-substituents can be better understood when their binding modes in the ribosomal tunnel are considered rather than their common low lipophilicity and excellent water solubility.

Fabrication of chitosan-bis (4-formyl-2 methoxy phenyl carbonate) Schiff base nanoparticles and evaluation of their antioxidant and anticancer properties.

The present study details on the mechanism of synthesis of bis (4-formyl-2 methoxy phenyl carbonate), using two green reagents dimethyl carbonate and vanillin for application as therapeutic agent. The synthesized FMPC was identified from the 13C nuclear magnetic resonance spectra. The novel modified Schiff base nanoparticles resulted from the crosslinking of FMPC with chitosan were confirmed by cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy. The incorporation of the FMPC was identified from the amorphous X-ray diffraction patterns of C-FMPC-Nps. The thermal stability of the formed nanoparticles was predicted using thermogravimetric analysis. The morphology of the nanoparticles as observed from HRTEM was found to be smooth and spherical in nature. Both FMPC and C-FMPC-Nps showed significant radical scavenging potential and anticancer property. The carbonate ester backbone and the moiety present in chitosan-FMPC-nanoparticles, underwent hydrolysis at the targeted cancer causing microenvironment to release vanillin and chitosan and enhance the anticancer activity. Both FMPC and C-FMPC-Nps exhibits a dose dependent cytotoxicity towards the different cell lines and it was tested with a commercial drug for application studies. Effective synthesis of FMPC, successful incorporation onto chitosan nanoparticles for the formation of C-FMPC-Nps. The formed Schiff base compound proves to have enhanced antioxidant and anticancer efficacy.

Characterization and Structure⁻Property Relationships of Organic⁻Inorganic Hybrid Composites Based on Aluminum⁻Magnesium Hydroxycarbonate and Azo Chromophore.

In this study, novel organic⁻inorganic composites were prepared by the complexation of dicarboxylic azo dye (AD) with aluminum⁻magnesium hydroxycarbonate (AlMg⁻LH). This procedure provides an effective method for the stabilization of dicarboxylic organic chromophores on an AlMg-LH host. The structures of the hybrid composites were examined by X-ray diffraction (XRD), secondary ion mass spectrometry (TOF-SIMS), 27-Al solid-state nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA) and scanning transmission electron microscopy (STEM). The TOF-SIMS method was applied to investigate the metal⁻dye interactions and to monitor the thermal stability of the organic⁻inorganic complexes. Secondary ion mass spectrometry confirmed the presence of a characteristic peak for C18H10O5N2Mg22+, indicating that both carboxylic groups interacted with AlMg-LH by forming complexes with two Mg2+ ions. Modification with hybrid pigments affected the crystal structure of the AlMg-LH mineral, as shown by the appearance of new peaks on the X-ray diffraction patterns. Adsorption of the dicarboxylic chromophore not only led to significantly enhanced solvent resistance but also improved the thermal and photostability of the hybrid pigments. We propose a possible arrangement of the azo dye in the inorganic matrix, as well as the presumed mechanism of stabilization.

Diarylcarbonates are a new class of deubiquitinating enzyme inhibitor.

Promiscuous inhibitors of tyrosine protein kinases, proteases and phosphatases are useful reagents for probing regulatory pathways and stabilizing lysates as well as starting points for the design of more selective agents. Ubiquitination regulates many critical cellular processes, and promiscuous inhibitors of deubiquitinases (DUBs) would be similarly valuable. The currently available promiscuous DUB inhibitors are highly reactive electrophilic compounds that can crosslink proteins. Herein we introduce diarylcarbonate esters as a novel class of promiscuous DUB inhibitors that do not have the liabilities associated with the previously reported compounds. Diarylcarbonates stabilize the high molecular weight ubiquitin pools in cells and lysates. They also elicit cellular phenotypes associated with DUB inhibition, demonstrating their utility in ubiquitin discovery. Diarylcarbonates may also be a useful scaffold for the development of specific DUB inhibitors.

Ultra-Fast Degradation of p-Aminophenol by a Nanostructured Iron Catalyst.

Full degradation of p-aminophenol in aqueous solution at room temperature by using a heterogeneous nanostructured iron hybrid catalyst in the presence of hydrogen peroxide is described. A nanostructured iron catalyst was prepared by in situ formation of iron carbonate nanorods on the protein network using an aqueous solution of an enzyme, lipase B from Candida antarctica (CAL-B). A second kind of iron nanostructured catalyst was obtained by the sunsequent treatment of the hybrid with an aqueous liquid extract of Mentha x piperita. Remarkable differences were observed using TEM imaging. When M. piperita extract was used, nanoparticles appeared instead of nanorods. Catalytic activity of these iron nanocatalysts was studied in the degradation of the environmental pollutant p-aminophenol (pAP) under different operating parameters, such as pH, presence of buffer or hydrogen peroxide concentration. Optimal conditions were pH 4 in acetate buffer 10 mM containing 1% (v/v) H2O2 for FeCO3NRs@CALB, while for FeCO3NRs@CALB-Mentha, water containing 1% (v/v) H2O2, resulted the best. A complete degradation of 100 ppm of pAP was achieved in 2 and 3 min respectively using 1 g Fe/L. This novel nanocatalyst was recycled five times maintaining full catalytic performance.

Study on the removal effect and influencing factors of nitrobenzene reduction by iron carbonate precipitates.

To investigate the activity of iron carbonate precipitates produced by long-term operation of Fe0 permeable reactive barriers, three kinds of precipitates, namely Fe6(OH)12CO3, Fe2(OH)2CO3, and FeCO3, were prepared to reduce the pollutant nitrobenzene. We studied the reduction effects of these iron carbonate precipitates on nitrobenzene by considering three factors, namely the initial nitrobenzene concentration, initial pH, and precipitate dosage, and established the kinetic degradation using pseudo-first-order kinetics model. The results showed that all three precipitates can reduce nitrobenzene, and the order of reducing capability is Fe6(OH)12CO3 > Fe2(OH)2CO3 > FeCO3; moreover, the removal efficiency values of nitrobenzene are 68.08, 53.00, and 50.29%. A high initial nitrobenzene concentration and high pH value are beneficial to nitrobenzene reduction, and removal efficiency was increased when pH was increased from 4 to 9. In addition, the increased precipitate addition in the Fe6(OH)12CO3 and Fe2(OH)2CO3 systems increased removal efficiency. Furthermore, the dosage did not significantly influence the removal rate in the FeCO3 system. Fe6(OH)12CO3 and Fe2(OH)2CO3 mainly relied on the precipitate itself with the structural Fe(II) to reduce nitrobenzene, and FeCO3 mainly relied on the dissolved Fe2+. The reaction of all three precipitates in reducing nitrobenzene followed the first-order reaction kinetics.

A novel process for CO2 capture by using sodium metaborate. Part I: effects of calcination.

This paper presents a comprehensive study on the carbonation of sodium metaborate (NaBO2) and the synthesis of high added value chemicals via NaBO2 and carbon dioxide (CO2). Carbon dioxide (CO2) is a greenhouse gas and NaBO2 is a by-product of sodium borohydride (NaBH4) hydrolysis reaction to produce H2. Therefore their transformation into commercial chemicals is quite important in order to provide a mutual benefit to global warming issue and hydrogen economy. In the presented study, reaction parameters such as hydration factor, furnace type, calcination temperature, and environment are investigated at different levels and optimized. The effects of those key parameters on CO2 fixation yield are discussed. It is found that 400 °C is a key temperature for dehydration and reaction steps. Both dehydrated NaBO2 is obtained and maximum carbonation conversion is reached at 400 °C. Moreover, at relatively low temperatures (below 400 °C), a new reaction pathway is proposed and proved by thermodynamic calculations. Structural properties of NaBO2 are exhibited differences regard to thermal exposure and the conversion is strictly related to the structural properties.

Oxidation-Responsive Aliphatic Polycarbonates from N-Substituted Eight-Membered Cyclic Carbonate: Synthesis and Degradation Study.

Oxidation-responsive aliphatic polycarbonates represent a promising branch of functional biodegradable polymers. This paper reports the synthesis and ring-opening polymerization (ROP) of an eight-membered cyclic carbonate possessing phenylboronic pinacol ester (C3) and the H2 O2 -triggered degradation of its polymer (PC3). C3 is prepared from the inexpensive and readily available diethanolamine with a moderate yield and undergoes the well-controlled anionic ROP with a living character under catalysis of 1,8-diazabicyclo[5.4.0]undec-7-ene. It can also be copolymerized with l-lactide, trimethylene carbonate, and 5-ter-butyloxycarbonylamino trimethylene carbonate, affording the copolymers with a varied distribution of the repeating units. To clearly demonstrate the oxidative degradation mechanism of PC3, this paper first investigates the H2 O2 -induced decomposition of small-molecule model compounds by proton nuclear magnetic resonance (1 H NMR). It is found that the adduct products formed by the in-situ-generated secondary amines and p-quinone methide (QM) are thermodynamically unstable and can decompose slowly back to QM and the amines. On this basis, this paper further studies the H2 O2 -accelerated degradation of PC3 nanoparticles that are prepared by the o/w emulsion method. A sequential process of oxidation of the phenylboronic ester, 1,6-elimination of the in-situ-generated phenol, releasing CO2 and intramolecular cyclization or isomerization is proposed as the degradation mechanism of PC3.

Poly(ethylene glycol)s as Ligands in Calcium-Catalyzed Cyclic Carbonate Synthesis.

Herein the use of CaI2 in combination with poly(ethylene glycol) dimethyl ether (PEG DME 500) as an efficient catalyst system for the addition of CO2 to epoxides is reported. This protocol is based on a nontoxic and abundant metal in conjunction with a polymeric ligand. Fifteen terminal epoxides were converted at room temperature to give the desired products in yields up to 99 %. Notably, this system was also effective for the synthesis of twelve challenging internal carbonates in yields up to 98 %.

Arsenate removal from aqueous solution by siderite synthesized under high temperature and high pressure.

In present study, a novel method was developed to synthesize siderite under high temperature and high pressure (SID-HTP). SID-HTP was characterized by N2 adsorption-desorption isotherms (BET), XRD, SEM, and FTIR and utilized to remove arsenic(V) (As(V)) from aqueous solution. Results showed that, under oxic condition, pH had ignorable effect on As(V) adsorption. However, adsorption capacity increased with increasing pH from 2 to 7 and remained relatively constant at higher pH until 10 under anoxic condition. Higher adsorption was obtained in the presence of oxygen, showing oxygen-enhanced As(V) adsorption on SID-HTP. In both cases, adsorption equilibrium was achieved within 12 h and adsorption process was better described by pseudo-second-order kinetic model. The equilibrium data fitted well with Langmuir isotherm model for As(V) adsorption. The maximum adsorption capacity increased with increasing temperature, which was up to 42 mg g-1 at 55 °C in the presence of oxygen. Thermodynamic study revealed that the adsorption was a spontaneous and endothermic process. The mechanism of oxygen-enhanced adsorption was mainly ascribed to the -OH on the surface of FeOOH (goethite and lepidocrocite) in the SID-HTP. It suggested that SID-HTP would be a potentially attractive adsorbent for As(V) removal.

Polyimidazolium Salts: Robust Catalysts for the Cycloaddition of Carbon Dioxide into Carbonates in Solvent-Free Conditions.

There is a growing interest in sustainable heterogeneous catalysts based on organic polymers. Here, we describe a series of polyimidazolium salt catalysts, prepared from the direct reaction of arene-bridged bis- and tris-alkyl halides with trimethylsilylimidazole. The polyimidazolium salts were characterized by spectroscopic and analytical techniques and it was found that their morphology and porosity could be controlled by adjusting the steric parameters of the spacer in the alkyl-halide starting materials. Moreover, the polymers are excellent heterogeneous organocatalysts for the cycloaddition of CO2 to epoxides to afford cyclic carbonates at atmospheric pressure under solvent-free conditions. The polymer catalysts exhibit long-term stability and may be recycled and reused at least 10 times.

Recent Developments in the Synthesis of Cyclic Carbonates from Epoxides and CO2.

The use of CO2 as a C1 building block will be of essential importance in the future. In this context the synthesis of cyclic carbonates from epoxides and CO2 gained great attention recently. These products are valuable compounds in a variety of chemical fields. The development of new catalysts and catalytic systems for this atom-economic, scalable, and industrially relevant reaction is a highly active research field. Over the past 17 years great advances have been made in this area of research. This chapter covers the survey of the important known classes of homogeneous catalysts for the addition of CO2 to epoxides. Besides pioneering work, recent developments and procedures that allow this transformation under mild reaction conditions (reaction temperatures of ≤100 °C and/or CO2 pressures of 0.1 MPa) are especially emphasized.

Charged Metalloporphyrin Polymers for Cooperative Synthesis of Cyclic Carbonates from CO2 under Ambient Conditions.

A facile and one-pot synthesis of metalloporphyrin-based ionic porous organic polymers (M-iPOPs) was performed through a typical Yamamoto-Ullmann coupling reaction for the first time. We used various characterization techniques to demonstrate that these strongly polar Al-based materials (Al-iPOP) possessed a relatively uniform microporosity, good swellable features, and a good CO2 capture capacity. If we consider the particular physicochemical properties, heterogeneous Al-iPOP, which bears both a metal active center and halogen anion, acted as a bifunctional catalyst for the solvent- and additive-free synthesis of cyclic carbonates from various epoxides and CO2 with an excellent activity and good recyclability under mild conditions. Interestingly, these CO2 -philic materials could catalyze the cycloaddition reaction smoothly by using simulated flue gas (15 % CO2 in N2 , v/v) as a raw material, which indicates that a stable local microenvironment and polymer swellability might promote the transformation. Thus, the introduction of polar ionic liquid units into metalloporphyrin-based porous materials is regarded as a promising new strategy for the chemical conversion of CO2 .

Synthesis and enhanced bone regeneration of carbonate substituted octacalcium phosphate.

Using a wet method, we have synthesized octacalcium phosphate carbonate, in which HPO42- in octacalcium phosphate is replaced with CO32-. The physical, crystal, and chemical properties of this new material were compared to octacalcium phosphate, Ca-deficient hydroxyapatite, and Ca-deficient carbonate apatite using X-ray diffraction, Fourier-transform infrared spectroscopy, inductively coupled plasma spectroscopy, and scanning electron microscopy. Surface roughness and morphology were also characterized, along with the ability to support proliferation and differentiation of MG63 cells, as measured by MTT and alkaline phosphatase assay. We found that octacalcium phosphate carbonate enhanced osteoblast proliferation more strongly than all other materials tested. Similarly, Ca-deficient carbonate apatite, a hydrolysate of octacalcium phosphate carbonate, stimulated osteoblast differentiation to a better extent than Ca-deficient hydroxyapatite, a carbonate-free hydrolysate of octacalcium phosphate. These results indicate that octacalcium phosphate carbonate has good biocompatibility and osteoconduction, and incorporation of carbonate into octacalcium phosphate and apatite enhances bone regeneration.

2-Pyridinyl Thermolabile Groups as General Protectants for Hydroxyl, Phosphate, and Carboxyl Functions.

Application of 2-pyridinyl thermolabile protecting groups (2-PyTPGs) for protection of hydroxyl, phosphate, and carboxyl functions is presented in this unit. Their characteristic feature is a unique removal process following the intramolecular cyclization mechanism and induced only by temperature rise. Deprotection rate of 2-PyTPGs is dependent on certain parameters, such as solvent (aqueous or non-aqueous medium), pH values, and electron distribution in a pyridine ring. The presented approach pertains not only to protecting groups but also to an advanced system of controlling certain properties of 2-pyridinyl derivatives. We improved the "chemical switch" method, allowing us to regulate the protecting group stability by inversing the electron distribution in 2-PyTPG. Together with pH values manipulation, this allows us to regulate the protecting group stability. Moreover, phosphite cyclization to oxazaphospholidine provides a very stable but easily reversible tool for phosphate protection/modifications. For all TPGs we confirmed their utility in a system of protecting groups. This concept can contribute to designing the general protecting group that could be useful in bioorganic chemistry. © 2017 by John Wiley & Sons, Inc.

Synthesis of Carbonates from Alcohols and CO2.

Alcohols are ubiquitous compounds in nature that offer modular building blocks for synthetic chemistry. Here we discuss the most recent development of different classes of alcohols and their coupling chemistry with carbon dioxide as to afford linear and cyclic carbonates, the challenges associated with their formation, and the potential of this chemistry to revive a waste carbon feed stock.

Synthesis of Asymmetrical Organic Carbonates using CO2 as a Feedstock in AgCl/Ionic Liquid System at Ambient Conditions.

Synthesis of asymmetrical organic carbonates from the renewable and inexpensive CO2 is of great importance but also challenging, especially at ambient conditions. Herein, we found that some metal salt/ionic liquid catalyst systems were highly active for the synthesis of asymmetrical organic carbonates from CO2 , propargylic alcohols, and primary alcohols. Especially, the AgCl/1-butyl-3-methylimidazolium acetate ([Bmim][OAc]) system was very efficient for the reactions of a wide range of substrates at room temperature and atmospheric pressure, and the yields of the asymmetrical organic carbonates could approach 100 %. The catalyst system could be reused at least five times without changing its catalytic performance, and could be easily recovered and reused. A detailed study indicated that AgCl and [Bmim][OAc] catalyzed the reactions cooperatively, resulting in unique catalytic performance.

Bifunctional Ionic Liquids Derived from Biorenewable Sources as Sustainable Catalysts for Fixation of Carbon Dioxide.

A series of highly efficient, bifunctional ionic liquids containing a quaternary alkyl ammonium cation and an amine anion were prepared from choline and amino acids, respectively. Nine ILs were synthesized, characterized, and applied as organocatalysts for the chemical fixation of carbon dioxide to form cyclic carbonates and quinazoline-2,4(1 H,3 H)-diones. A binary mixture of an IL and a co-catalysts generates deep eutectic solvents (DESs) and accelerates the rate of the cycloaddition reaction at atmospheric pressure and low temperature (70 °C). The presence of the hydroxyl functional group of choline and the free amine group of the amino acids in the ILs has a synergistic effect on the activation of the epoxide and carbon dioxide towards the cycloaddition reactions. These ILs are biodegradable and are synthesized from easily available biorenewable sources. Additionally, this catalytic method demonstrates ultimate environmental benignity because of the mild metal- and solvent-free conditions as well as the recyclability of the catalyst and co-catalyst.