Controlled Synthesis of Asymmetric Dialkyl and Cyclic Carbonates Using the Highly Selective Reactions of Imidazole Carboxylic Esters

Use of carbonyldiimidazole as a derivatization agent for the detection of pinacolyl alcohol, a forensic marker for Soman, by EI-GC-MS and LC-HRMS in official OPCW proficiency test matrices

Pinacolyl alcohol (PA), a key forensic marker for the nerve agent Soman (GD), is a particularly difficult analyte to detect by various analytical methods. In this work, we have explored the reaction between PA and 1,1'-carbonyldiimidazole (CDI) to yield pinacolyl 1H-imidazole-1-carboxylate (PIC), a product that can be conveniently detected by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high-resolution mass spectrometry (LC-HRMS). Regarding its GC-MS profile, this new carbamate derivative of PA possesses favorable chromatographic features such as a sharp peak and a longer retention time (RT = 16.62 min) relative to PA (broad peak and short retention time, RT = 4.1 min). The derivative can also be detected by LC-HRMS, providing an avenue for the analysis of this chemical using this technique where PA is virtually undetectable unless present in large concentrations. From a forensic science standpoint, detection of this low molecular weight alcohol signals the past or latent presence of the nerve agent Soman (GD) in a given matrix (i.e., environmental or biological). The efficiency of the protocol was tested separately in the analysis and detection of PA by EI-GC-MS and LC-HRMS when present at a 10 μg/mL in a soil matrix featured in the 44th PT and in a glycerol-rich liquid matrix featured in the 48th Official Organization for the Prohibition of Chemical Weapons (OPCW) Proficiency Test when present at a 5 μg/mL concentration. In both scenarios, PA was successfully transformed into PIC, establishing the protocol as an additional tool for the analysis of this unnatural and unique nerve agent marker by GC-MS and LC-HRMS.

A facile method to control the phase behavior of hydroxypropyl cellulose

We report a facile chemical method to convert the hydroxyl groups of hydroxypropyl cellulose (HPC) into carbamates. It was achieved by the reaction of HPC with N-methyl carbamoylimidazole, which is a safe and easy to handle replacement for the particularly hazardous reagent methyl isocyanate. Using a series of HPC with a range of molar substitution of hydroxypropyl groups, we synthesized HPC methylcarbamates showing lower critical solution temperature (LCST) in the range between 94 and 15 °C. A linear dependence of LCST versus methylcarbamate degree of substitution is observed. The lower the initial hydroxypropyl content of HPC, the greater the effect of methylcarbamate on the LCST. Surface tension study showed that methylcarbamate modification has an insignificant effect on the hydrophilic-hydrophobic balance of the macromolecules below LCST unless the molecular substitution of hydroxypropyl groups is so low (0.8) that the native cellulose OH groups can react with N-methyl carbamoylimidazole.

Degradable Copolymer Nanoparticles from Radical Ring-Opening Copolymerization between Cyclic Ketene Acetals and Vinyl Ethers

2-Methylene-1,3-dioxepane (MDO) and different vinyl ether (VE) monomers were successfully copolymerized by free-radical radical ring-opening copolymerization (rROP) to yield P(MDO- co-VE) copolymers with M_n = 7 000-13 000 g·mol^-1 and high molar fractions of MDO ( F_MDO = 0.7-0.9). By using VE derivatives of different aqueous solubilities or by grafting PEG chains onto the copolymers by "click" chemistry via azide-containing VE units, hydrophobic, amphiphilic and water-soluble copolymers were obtained. The different copolymers were then formulated into nanoparticles by nanoprecipitation using Pluronics for hydrophobic copolymers, without surfactant for amphiphilic copolymers, or blended with PMDO for water-soluble copolymers. Most of the copolymers led to nanoparticles with average diameters in the 130-250 nm with narrow particle size distributions and satisfying colloidal stability for a period of at least 1-2 weeks and up to 6 months. The copolymers were successfully degraded under accelerated, hydrolytic or enzymatic conditions. Hydrophobic copolymers led to degradation kinetics in PBS similar to that of PCL and complete degradation (-95% in M_n decrease) was observed in the presence of enzymes (lipases). Preliminary cytotoxicity assays were performed on endothelial cells (HUVEC) and macrophages (J774.A1) and revealed high cell viabilities at 0.1 mg·mL^-1.

Fluoride-promoted carbonylation polymerization: a facile step-growth technique to polycarbonates

Fluoride-Promoted Carbonylation (FPC) polymerization is herein presented as a novel catalytic polymerization methodology that complements ROP and unlocks a greater synthetic window to advanced polycarbonates. The overall two-step strategy is facile, robust and capitalizes on the synthesis and step-growth polymerization of bis-carbonylimidazolide and diol monomers of 1,3- or higher configurations. Cesium fluoride (CsF) is identified as an efficient catalyst and the bis-carbonylimidazolide monomers are synthesized as bench-stable white solids, easily obtained on 50-100 g scales from their parent diols using cheap commercial 1,1'-carbonyldiimidazole (CDI) as activating reagent. The FPC polymerization works well in both solution and bulk, does not require any stoichiometric additives or complex settings and produces only imidazole as a relatively low-toxicity by-product. As a proof-of-concept using only four diol building-blocks, FPC methodology enabled the synthesis of a unique library of polycarbonates covering (i) rigid, flexible and reactive PC backbones, (ii) molecular weights 5-20 kg mol^-1, (iii) dispersities of 1.3-2.9 and (iv) a wide span of glass transition temperatures, from -45 up to 169 °C.

Tough and degradable photopolymers derived from alkyne monomers for 3D printing of biomedical materials

Photo curing of low-cytotoxic alkyne carbonate/thiol formulations leads to tough polymers with adjustable degradation behavior for 3D printing of biomedical devices.

Green chain-shattering polymers based on a self-immolative azobenzene motif

A chain-shattering polymer system consisting of nontoxic, partially renewable resource-based monomersviaacyclic diene metathesis (ADMET) chemistry is introduced.

Development of highly sensitive and selective antibodies for the detection of the explosive pentaerythritol tetranitrate (PETN) by bioisosteric replacement

An improved antibody against the explosive pentaerythritol tetranitrate (PETN) was developed. The immunogen was designed by the concept of bioisosteric replacement, which led to an excellent polyclonal antibody with extreme selectivity and immunoassays of very good sensitivity. Compounds such as nitroglycerine, 2,4,6-trinitrotoluene, 1,3,5-trinitrobenzene, hexogen (RDX), 2,4,6-trinitroaniline, 1,3-dinitrobenzene, octogen (HMX), triacetone triperoxide, ammonium nitrate, 2,4,6-trinitrophenol and nitrobenzene were tested for potential cross-reactivity. The detection limit of a competitive enzyme-linked immunosorbent assay was determined to be around 0.5 µg/l. The dynamic range of the assay was found to be between 1 and 1000 µg/l, covering a concentration range of three decades. This work shows the successful application of the bioisosteric concept in immunochemistry by exchange of a nitroester to a carbonate diester. The antiserum might be used for the development of quick tests, biosensors, microtitration plate immunoassays, microarrays and other analytical methods for the highly sensitive detection of PETN, an explosive frequently used by terrorists, exploiting the extreme difficulty of its detection.

Synthesis, nanoprecipitation and pH sensitivity of amphiphilic linear-dendritic hybrid polymers and hyperbranched-polydendrons containing tertiary amine functional dendrons

The combination of linear polymers with dendritic chain-ends has led to numerous studies of linear-dendritic polymer hybrid materials. Interchain branching within the linear segment of these materials has recently extended this concept to the formation of soluble hyperbranched-polydendrons. Here, the introduction of amphiphilicity into hyperbranched-polydendrons has been achieved for the first time through the use of tertiary amine functional dendritic chain-ends and branched hydrophobic polymer segments. The synthesis and aqueous nanoprecipitation of these branched materials is compared with their linear-dendritic polymer analogues, showing that chain-end chemistry/generation, precipitation medium pH and polymer architecture are all capable of influencing the ability to generate nanoparticles, the resulting nanoparticle diameter and dispersity, and subsequent response to changes in pH.

Cellulose carbonates: a platform for promising biopolymer derivatives with multifunctional capabilities

Cellulose carbonates as a platform compound open new possibilities for the design of advanced materials based on the most important renewable resource cellulose. In the present feature, the chemistry of cellulose carbonates is discussed considering own research results adequately. After a short overview about methods for activation of polysaccharides for a conversion with nucleophilic compounds in particular with amines, details about various methods for the synthesis of polysaccharide carbonates are discussed. The main issue of the feature is the synthesis and aminolysis of cellulose carbonates with low, intermediate, and high degree of substitution and the evaluation of this chemistry with respect to specific challenges. Functional cellulose carbamates, obtained from cellulose phenyl carbonate by aminolysis, show the potential use of this class of celluloses. Immunoassays and zwitterionic polymers are included as representative examples regarding properties and application of the new cellulose-based products.

Biological evaluation and molecular modelling of didanosine derivatives

These prodrugs of DDI with increased lipophilicity and good antiviral performance should be of interest in HIV therapy.

Reactive imidazole intermediates: simplified synthetic approach to functional aliphatic cyclic carbonates

Reactive imidazole intermediates based on AB₂ and A₃ monomers, i.e. bis(methylol) propionic acid (bis-MPA) and trimethylolpropane (TMP) have successfully been synthesized and isolated on a 100 gram scale via a facile synthetic protocol using 1,1′-carbonyldiimidazole (CDI) as a key reagent.

Practical synthesis of β-oxo benzo[d]thiazolyl sulfones: scope and limitations

In this paper, we discuss our new synthetic approach towards functionalized benzo[d]thiazolyl (BT) sulfones, based on the reunion of alkyl BT sulfones and various electrophiles (e.g. R-CO-X, RO-CO-X, RS-CO-X, Ts-X…). All important aspects of this coupling reaction, including relevant and undesirable side reactions, are evaluated by means of calculations and competitive experiments. The scope and limitations of this method are established.

Synthesis and characterisation of polyamide dendrimers with systematically varying surface functionality

Remarkable changes of properties result from systematically varying the surface functionality of polyamide dendrimers within a single generation.

Inter- and intramolecular glycosylation of exo-glycals promoted by metallic Lewis acids

exo-Glycosyl carbonates were employed for inter- and intramolecular glycosylation reactions. A number of metallic Lewis Acids and solvents were examined to enhance the reactivity. The optimum conditions were found to be the use of AlCl3 in 1-nitropropane. The method was demonstrated to be useful for the intermolecular glycosyl transfer of several nucleophiles, including simple alcohols, sugars, and amino acid derivatives; however, intramolecular glycosylations were not successful.

Selective One-Pot Synthesis of Trithiocarbonates, Xanthates, and Dithiocarbamates for Use in RAFT/MADIX Living Radical Polymerizations

[reaction: see text] We report a facile route for the production of chain transfer agents for reversible addition fragmentation chain transfer (RAFT) and macromolecular design via the interchange of xanthates (MADIX) polymerizations, via a one-pot reaction. 1,1'-Thiocarbonyl diimidazole (TCDI) undergoes controlled monosubstitution when reacted with secondary thiols or alcohols. The intermediate S/O-esters of imidazole-N-thionocarboxylic acid react efficiently with a range of primary thiols, alcohols, and amines to form asymmetrical dithiocarbonates, trithiocarbonates, and dithiocarbamates, respectively. The synthesis provides a facile approach to the controlled radical polymerization of vinyl monomers through the reversible addition-fragmentation chain transfer (RAFT) mechanism.