Reactions of carbon disulfide with N-nucleophiles

Factors affecting the durability of dimethyl dithiocarbamate-stabilized air pollution control (APC) residues derived from municipal solid waste incineration

Sodium dimethyl dithiocarbamate (SDD) is widely used for stabilizing heavy metals to minimize pollution from air pollution control (APC) residues derived from municipal solid waste incineration. However, the effect of environmental conditions on heavy metal leaching from SDD-stabilized APC residues remains unknown. Therefore, this study aimed to evaluate the durability of SDD-stabilized APC residues and determine the relationship between heavy metal leaching and environmental factors, including pH, temperature, and oxygen. The results revealed that accelerated SDD decomposition and the decline in durability of SDD-stabilized APC residues were caused by acidic and aerated conditions and temperatures above 40 °C. A decrease in pH from 12.25 to 4.69 increased the Cd and Pb concentrations in SDD-stabilized APC residue leachate from below detection (0.002 mg/L) to 1.32 mg/L and 0.04 mg/L to 3.79 mg/L, respectively. Heating at 100 °C for 2 d increased the Cd and Pb concentrations from below detection (0.002 mg/L and 0.01 mg/L) to 2.96 mg/L and 0.47 mg/L, respectively. Aeration for 5 d increased the Cd and Pb concentrations from below detection to 0.09 mg/L and 0.49 mg/L, respectively. The decline in durability was attributed to acid hydrolysis, thermal decomposition, and oxidative damage of SDD, resulting in breakage of the chelated sulfur-metal bond, which was confirmed by the decrease in the oxidizable fraction of heavy metals and the SDD content. This study improves the understanding of the factors contributing to the decline in durability of heavy metals in SDD-stabilized APC residues, which is important for ensuring the long-term stabilization and environmental safety of these residues.

Diaryl dithiocarbamates: synthesis, oxidation to thiuram disulfides, Co(III) complexes [Co(S2CNAr2)3] and their use as single source precursors to CoS2

Air and moisture stable diaryl dithiocarbamate salts, Ar₂NCS₂Li, result from addition of CS₂ to Ar₂NLi, the latter being formed upon deprotonation of diarylamines by ⁿBuLi. Oxidation with K₃[Fe(CN)₆] affords the analogous thiuram disulfides, (Ar₂NCS₂)₂, two examples of which (Ar = p-C₆H₄X; X = Me, OMe) have been crystallographically characterised. The interconversion of dithiocarbamate and thiuram disulfides has also been probed electrochemically and compared with that established for the widely-utilised diethyl system. While oxidation reactions are generally clean and high yielding, for Ph(2-naphthyl)NCS₂Li an ortho-cyclisation product, 3-phenylnaphtho[2,1-d]thiazole-2(3H)-thione, is also formed, resulting from a competitive intramolecular free-radical cyclisation. To demonstrate the coordinating ability of diaryl dithiocarbamates, a small series of Co(III) complexes have been prepared, with two examples, [Co{S₂CN(p-tolyl)₂}₃] and [Co{S₂CNPh(m-tolyl)}₃] being crystallographically characterised. Solvothermal decomposition of [Co{S₂CN(p-tolyl)₂}₃] in oleylamine generates phase pure CoS₂ nanospheres in an unexpected phase-selective manner.

Dithiocarbamate Complexes as Single Source Precursors to Nanoscale Binary, Ternary and Quaternary Metal Sulfides

Nanodimensional metal sulfides are a developing class of low-cost materials with potential applications in areas as wide-ranging as energy storage, electrocatalysis, and imaging. An attractive synthetic strategy, which allows careful control over stoichiometry, is the single source precursor (SSP) approach in which well-defined molecular species containing preformed metal-sulfur bonds are heated to decomposition, either in the vapor or solution phase, resulting in facile loss of organics and formation of nanodimensional metal sulfides. By careful control of the precursor, the decomposition environment and addition of surfactants, this approach affords a range of nanocrystalline materials from a library of precursors. Dithiocarbamates (DTCs) are monoanionic chelating ligands that have been known for over a century and find applications in agriculture, medicine, and materials science. They are easily prepared from nontoxic secondary and primary amines and form stable complexes with all elements. Since pioneering work in the late 1980s, the use of DTC complexes as SSPs to a wide range of binary, ternary, and multinary sulfides has been extensively documented. This review maps these developments, from the formation of thin films, often comprised of embedded nanocrystals, to quantum dots coated with organic ligands or shelled by other metal sulfides that show high photoluminescence quantum yields, and a range of other nanomaterials in which both the phase and morphology of the nanocrystals can be engineered, allowing fine-tuning of technologically important physical properties, thus opening up a myriad of potential applications.

Direct amide formation in a continuous-flow system mediated by carbon disulfide

We report a direct flow-based synthesis of amides. The developed approach is prominently simple and various aliphatic and aromatic amides were synthetized with excellent yields. The technology is considerably robust and easy scale-up was carried out.

(Z)-Tetrahydrothiophene and (Z)-tetrahydrothiopyran synthesis through nucleophilic substitution and intramolecular cycloaddition of alkynyl halides and EtOCS2K

This protocol provides a novel, environmentally friendly and simple method for the synthesis of (Z)-tetrahydrothiophene derivatives using the nucleophilic thiyl radical intramolecular cycloaddition cascade process to construct C-S bonds under transition-metal-free conditions. This transformation process offers a broad substrate scope, good functional group tolerance, and excellent stereoselectivity (Z/E ratios up to 99/1). Moreover, the process uses odourless, stable and cheap EtOCS2K as the sulfur source.

Spirocyclic and Bicyclic 8-Nitrobenzothiazinones for Tuberculosis with Improved Physicochemical and Pharmacokinetic Properties

8-Nitrobenzothiazinones (BTZs) typified by the second-generation analogue PBTZ169 are a new class of antitubercular agents. The activity of BTZs and lipophilicity are tightly coupled since the molecular target DprE1 is located in the mycobacterial cell envelope. A series of analogues was designed to address the notorious insolubility of the BTZs while preserving the required lipophilicity. This was accomplished by decreasing the molecular planarity and symmetry through bioisosteric replacement of the piperazine moiety of PBTZ169 with spirocyclic and bicyclic diamines. Several promising compounds with improved aqueous solubilities were identified with potent antitubercular activity. Compound 5 was identified as the most promising candidate based on its excellent antitubercular activity (MIC of 32 nM), more than 1000-fold improvement in solubility, 2-fold lower clearance in mouse and human microsomes relative to PBTZ169, and promising pharmacokinetic parameters.

Xanthate-mediated synthesis of (E)-alkenes by semi-hydrogenation of alkynes using water as the hydrogen donor

Semi-hydrogenation of alkynes is one of the most widely used methods for obtaining alkenes in laboratory preparation and in industry. Transition metal catalysts have been extensively studied for this transformation, but the tolerance of functional groups, such as pyridine, -OH, -NH2, -Bpin, and halides, and the toxicity of the trace amount of transition metal catalysts are still highly challenging. In this study, we report a general and robust strategy to achieve the semi-hydrogenation of alkynes using inexpensive and commercially available xanthate as the mediator. Mechanism studies support a non-radical process and H2O acts as the hydrogen donor.

Cooperative adsorption of carbon disulfide in diamine-appended metal-organic frameworks

Over one million tons of CS₂ are produced annually, and emissions of this volatile and toxic liquid, known to generate acid rain, remain poorly controlled. As such, materials capable of reversibly capturing this commodity chemical in an energy-efficient manner are of interest. Recently, we detailed diamine-appended metal–organic frameworks capable of selectively capturing CO₂ through a cooperative insertion mechanism that promotes efficient adsorption–desorption cycling. We therefore sought to explore the ability of these materials to capture CS₂ through a similar mechanism. Employing crystallography, spectroscopy, and gas adsorption analysis, we demonstrate that CS₂ is indeed cooperatively adsorbed in N,N-dimethylethylenediamine-appended M₂(dobpdc) (M = Mg, Mn, Zn; dobpdc^4- = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate), via the formation of electrostatically paired ammonium dithiocarbamate chains. In the weakly thiophilic Mg congener, chemisorption is cleanly reversible with mild thermal input. This work demonstrates that the cooperative insertion mechanism can be generalized to other high-impact target molecules.

The large-scale production of CS₂ presents both environmental and biological hazards, yet adsorbents capable of CS₂ capture remain scarcely explored. Here, Long and colleagues demonstrate that CS₂ is adsorbed in diamine-appended metal–organic frameworks through a cooperative and chemically specific insertion process.

An innovative and efficient route to the synthesis of metal-based glycoconjugates: proof-of-concept and potential applications

With a view to developing more efficient strategies to the functionalization of metallodrugs with carbohydrates, we here report on an innovative and efficient synthetic route to generate gold(iii) glycoconjugates in high yields and purity. The method is based on the initial synthesis of the zinc(ii)-dithiocarbamato intermediate [Zn^II(SSC-Inp-GlcN)₂] (Inp = isonipecotic moiety; GlcN = amino-glucose) followed by the transfer of the glucoseisonipecoticdithiocarbamato ligand to the gold(iii) center via transmetallation reaction between the zinc(ii) intermediate and K[Au^IIIBr₄] in 1 : 2 stoichiometric ratio, yielding the corresponding glucose-functionalized gold(iii)-dithiocarbamato derivative [Au^IIIBr₂(SSC-Inp-GlcN)]. No protection/deprotection of the amino-glucose scaffold and no chromatographic purification were needed. The synthetic protocol was optimized for glucose precursors bearing the amino function at either the C² or the C⁶ position, and works in the case of both α and β anomers. The application of the synthetic strategy was also successfully extended to other metal ions of biomedical interest, such as gold(i) and platinum(ii), to obtain [Au^I(SSC-Inp-GlcN)(PPh₃)] and [Pt^II(SSC-Inp-GlcN)₂], respectively. All compounds were fully characterized by elemental analysis, mid- and far-IR, mono- and multidimensional NMR spectroscopy, and, where possible, X-ray crystallography. Results and potential applications are here discussed.

Copper-Catalyzed Aerobic Oxidative Reaction of C60 with Aliphatic Primary Amines and CS2

A novel type of fullerene derivatives, [60]fullerothiazolidinethiones (2), were obtained from the copper-catalyzed aerobic oxidative reaction of C₆₀ with aliphatic primary amines and CS₂ in 4:1 v/v DMF and o-DCB. The obtained products were fully characterized with the X-ray single-crystal diffraction and spectroscopic methods. Control experiment with maleic anhydride, an analogue to C₆₀, also afforded thiazolidinethione product, but via a mechanism different from that of C₆₀ judging from the structure difference between the two types of thiazolidinethione compounds, demonstrating the unique reactivity of C₆₀.

Mechanochemical synthesis of thioureas, ureas and guanidines

In this review, the recent progress in the synthesis of ureas, thioureas and guanidines by solid-state mechanochemical ball milling is highlighted. While the literature is abundant on their preparation in conventional solution environment, it was not until the advent of solvent-free manual grinding using a mortar and pestle and automated ball milling that new synthetic opportunities have opened. The mechanochemical approach not only has enabled the quantitative synthesis of (thio)ureas and guanidines without using bulk solvents and the generation of byproducts, but it has also been established as a means to develop "click-type" chemistry for these classes of compounds and the concept of small molecule desymmetrization. Moreover, mechanochemistry has been demonstrated as an effective tool in reaction discovery, with emphasis on the reactivity differences in solution and in the solid state. These three classes of organic compounds share some structural features which are reflected in their physical and chemical properties, important for application as organocatalysts and sensors. On the other hand, the specific and unique nature of each of these functionalities render (thio)ureas and guanidines as the key constituents of pharmaceuticals and other biologically active compounds.

A facile and efficient procedure for the synthesis of new benzimidazole-2-thione derivatives

A series of benzimidazole-2-thione derivatives was synthesized using a reaction between the macrocyclic aminal 16H,13H-5:12,7:14-dimethanedibenzo[d,i]-[1,3,6,8] tetraazecine (DMDBTA, 5) and various nucleophiles in the presence of carbon disulfide. A full chemical characterization using IR, ¹H-, ¹³C-NMR and GC-MS analyses of the new compounds is provided. These compounds were separated from the reaction mixture by column chromatography (CC) in highly pure form in 15%-51.4% yield.

(1E,2E)-1,2-Bis(2,3,4-trimeth-oxy-benzyl-idene)hydrazine

The title compound, C(20)H(24)N(2)O(6), was obtained as an unexpected product by the reaction of hydrazinium dithio-carbazate with 2,3,4-trimeth-oxy-benzaldehyde in refluxing ethanol. The mol-ecule lies on a center of inversion. The crystal packing is stabilized by weak inter-molecular C-H⋯O inter-actions.