Altering Copper‐Catalyzed A3 Couplings by Mechanochemistry: One‐Pot Synthesis of 1,4‐Diamino‐2‐butynes from Aldehydes,Amines, and Calcium Carbide

The ability of mechanochemistry to alter established chemical selectivity is demonstrated. A copper(I)‐catalyzed mechanochemical aldehyde/alkyne/amine coupling using calcium carbide as the acetylene source provides selective access to 1,4‐diamino‐2‐butynes, which contrasts classical approaches that provide propargylamine‐type products. Solventless milling conditions were found to be essential to unmask A³ coupling products with new compositions.     

Altering Copper‐Catalyzed A3 Couplings by Mechanochemistry: One‐Pot Synthesis of 1,4‐Diamino‐2‐butynes from Aldehydes,Amines, and Calcium Carbide

The ability of mechanochemistry to alter established chemical selectivity is demonstrated. A copper(I)‐catalyzed mechanochemical aldehyde/alkyne/amine coupling using calcium carbide as the acetylene source provides selective access to 1,4‐diamino‐2‐butynes, which contrasts classical approaches that provide propargylamine‐type products. Solventless milling conditions were found to be essential to unmask A³ coupling products with new compositions.     

Using Calcium Carbide as an Acetylene Source for Cascade Synthesis of Pyrrolo[2,3‐b]quinoxalines via Copper‐Free Sonogashira Coupling Reaction

A palladium‐catalyzed cascade protocol has been established for the synthesis of 4‐methyl‐1‐(1H‐pyrrolo[2,3‐b]‐quinoxalin‐2‐yl)cyclohexanols and 2‐phenyl‐1‐(1H‐pyrrolo[2,3‐b]quinoxalin‐2‐yl)propan‐1‐ols through the reaction of N‐alkyl(aryl)‐3‐chloroquinoxalin‐2‐amines with calcium carbide and cyclohexanones or 2‐phenylpropanal. This one‐pot process, carried out without any copper salt in the key step of the Sonogashira coupling reaction, provides an efficient method for the synthesis of 2,3‐disubstituted pyrrolo[2,3‐b]quinoxalines in the presence of catalytic amounts of Pd(PPh₃)₂Cl₂ in DMSO/H₂O with high yields. The benefit of this strategy is the use of a commercially available, inexpensive, and less hazardous primary chemical feedstock, calcium carbide, as an acetylene source in a wet solvent.     

高校化学教学实验室小型试剂库改造

有机化学实验是培养学生掌握实验基本技能和技术、提高动手能力的必修课。有机化学实验产生的废液成分复杂,尽管目前广大师生的环保意识比较强,实验室废液能够做到分类收集并交由有资质的公司进行处理,但是完全依赖环保公司的处理成本比较高。因此我们尝试对有机化学实验室产生的废液进行实验室原点处理,真正做到谁污染、谁治理,有效降低废液的处理成本,并实现有机试剂的循环使用。     

Acetylene as a Dicarbene Equivalent for Gold(I) Catalysis: Total Synthesis of Waitziacuminone in One Step

The gold(I)‐catalyzed reaction of acetylene gas with alkenes leads to (Z,Z)‐1,4‐disubstituted 1,3‐butadienes and biscyclopropanes depending on the donor ligand on gold(I). Acetylene was generated in situ from calcium carbide and water in a user‐friendly procedure. Reaction of acetylene with 1,5‐dienes gives rise stereoselectively to tricyclo[5.1.0.0^2,4]octanes. This novel double cyclopropanation has been applied to the one step total synthesis of the natural product waitziacuminone from acetylene and geranyl acetone.     

The use of calcium carbide in one-pot synthesis of symmetric diaryl ethynes

An efficient Pd-catalyzed copper and amine free coupling reaction of acetylene and aryl bromides was achieved with calcium carbide as an acetylene source, using inorganic base and easily prepared, air-stable aminophosphine ligand in common organic solvents, providing symmetric diaryl ethynes in one-pot with yields ranged from moderate to excellent.     

Free Radical Synthetic Protocol for Benzothiazoles via Ring Opening of Benzotriazole: A Two‐step Organic Chemistry Experiment for Undergraduate and Postgraduate Students

The utility and advantages of benzotriazole methodology have been described for the practical synthesis of benzothiazoles. The two‐step synthetic procedure includes nucleophilic acyl substitution followed by benzotriazole ring cleavage under the free radical condition and subsequent cyclization via elimination of molecular nitrogen (N₂). This protocol requires cheap and readily available reagents, and moreover easy to handle, thus can be used to teach undergraduate and postgraduate students about the importance of benzotriazole moiety in organic synthesis, ring cleavage chemistry, cyclization reactions, and use of industrial waste in free radical reactions. Students can also learn some important and common techniques useful in organic chemistry such as monitoring of organic reaction using thin‐layer chromatography and UV, microwave (MW) technique for the synthesis, and column chromatography for the product isolation and structure determination through NMR, MS, and IR spectral analysis of the pure compounds.     

Topochemical Transformations of CaX2 (X=C,Si, Ge) to Form Free‐Standing Two‐Dimensional Materials

Topochemical transformations of layered materials CaX₂ (X=Si, Ge) are the method of choice for the high‐yield synthesis of pristine, defect‐free two‐dimensional systems silicane and germanane, which have advanced electronic properties. Based on solid‐state dispersion‐corrected calculations, mechanisms for such transformations are elucidated that provide an in‐depth understanding of phase transition in these layered materials. While formation of such layered materials is highly favorable for silicane and germanane, a barrier of 1.2 eV in the case of graphane precludes its synthesis from CaC₂ topochemically. The energy penalty required for distorting linear acetylene into a trans‐bent geometry accounts for this barrier. In contrast it is highly favorable in the heavier analogues, resulting in barrierless topochemical generation of silicane and germanane. Photochemical generation of the trans‐bent structure of acetylene in its first excited state (S₁) can directly generate graphane through a barrierless condensation. Unlike the buckled structure of silicene, the phase‐h of CaSi₂ with perfectly planar silicene layers exhibits the Dirac cones at the high symmetry points K and H. Interestingly, topochemical acidification of the cubic phase of calcium carbide is predicted to generate the previously elusive platonic hydrocarbon, tetrahedrane.     

Easy‐to‐Attach/Detach Solubilizing‐Tag‐Aided Chemical Synthesis of an Aggregative Capsid Protein

A solubilizing Trt‐K₁₀ tag was developed for the effective chemical preparation of peptides/proteins with low solubility. The Trt‐K₁₀ tag comprises a hydrophilic oligo‐Lys sequence and a trityl anchor, and can be selectively introduced to a side chain thiol of Cys of deprotected peptides/proteins with a trityl alcohol‐type introducing reagent Trt(OH)‐K₁₀ under acidic conditions. Significantly, the ligation product in the reaction mixture of a thiol‐additive‐free native chemical ligation can be modified directly in a one‐pot manner to facilitate the isolation of the product by high‐performance liquid chromatography. Finally, the Trt‐K₁₀ tag can be readily removed with a standard trifluoroacetic acid cocktail. Using this easy‐to‐attach/detach tag‐aided method, a hepatitis B virus capsid protein that is usually difficult to handle was synthesized successfully.     

Robust Ultramicroporous Metal–Organic Frameworks with Benchmark Affinity for Acetylene

Highly selective separation and/or purification of acetylene from various gas mixtures is a relevant and difficult challenge that currently requires costly and energy‐intensive chemisorption processes. Two ultramicroporous metal–organic framework physisorbents, NKMOF‐1‐M (M=Cu or Ni), offer high hydrolytic stability and benchmark selectivity towards acetylene versus several gases at ambient temperature. The performance of NKMOF‐1‐M is attributed to their exceptional acetylene binding affinity as revealed by modelling and several experimental studies: in situ single‐crystal X‐ray diffraction, FTIR, and gas mixture breakthrough tests. NKMOF‐1‐M exhibit better low‐pressure uptake than existing physisorbents and possesses the highest selectivities yet reported for C₂H₂/CO₂ and C₂H₂/CH₄. The performance of NKMOF‐1‐M is not driven by the same mechanism as current benchmark physisorbents that rely on pore walls lined by inorganic anions.     

Facile One‐Pot Synthesis of Monosubstituted 1‐Aryl‐1H‐1,2,3‐triazoles from Arylboronic Acids and Prop‐2‐ynoic Acid (=Propiolic Acid) or Calcium Acetylide (=Calcium Carbide) as Acetylene Source

The synthesis of monosubstituted 1‐aryl‐1H‐1,2,3‐triazoles was achieved in a one‐pot reaction from arylboronic acids and prop‐2‐ynoic acid or calcium acetylide (=calcium carbide), respectively, as a source of acetylene, with yields ranging from moderate to excellent (Scheme 1, Table 2). The reaction conditions were successfully applied to arylboronic acids, including analogs with various functionalities. Unexpectedly, the 1,2,3‐triazole moiety promoted a regioselective hydrodebromination (Scheme 2).     

A Hydrogen‐Bonded Organic Framework (HOF) with Type IV NH3 Adsorption Behavior

An S‐shaped gas isotherm pattern displays high working capacity in pressure‐swing adsorption cycle, as established for CO₂, CH₄, acetylene, and CO. However, to our knowledge, this type of adsorption behavior has not been revealed for NH₃ gas. Herein, we design and characterize a hydrogen‐bonded organic framework (HOF) that can adsorb NH₃ uniquely in an S‐shape (type IV) fashion. While conventional porous materials, mostly with type I NH₃ adsorption behavior, require relatively high regeneration temperature, this platform which has significant working capacity is easily regenerated and recyclable at room temperature.     

Controlled Chemical and Drug Delivery via the Internal and External Surfaces of Layered Compounds

Abstract

We demonstrate, and review the very small, but growing body of literature regarding a recently discovered application of layered compounds, which involves the ability of layered materials to sequester and later release molecules of chemical and biological significance. The application relies upon intercalation chemistry; a reversible process whereby atoms, molecules, macromolecules, and polymers may be inserted into the interstices of a layered matrix. We demonstrate that layered materials are able to effectively getter water‐soluble atoms and molecules from aqueous dispersions, and further demonstrate that the absorbed molecules can be later released from the interlayer region to perform a desired chemical function. Work in our laboratory involving the application of layered hybrid materials in photographic media is described in detail and we establish two general release mechanisms whereby intercalated functional chemistry can be first sequestrated and later delivered via a chemical switch to perform a desired function. The process has enormous potential as a general method for the controlled, temporal release of materials of chemical and biological significance.     

Alkynyl- and Alkenyl(phenyl)iodonium Compounds. New Synthetic Methods (86)

Compounds with highly coordinated, polyvalent main-group elements represent an interesting alternative to the many well-known transition-metal complexes. Among the oldest and best known stable examples of such organic molecules are the iodine(III) compounds. Diaryliodonium species, Ar₂IX, for example, have been known for over a hundred years and play an important role in lithography. Likewise, acetylenes and olefins are among the oldest, most important, and most valuable compounds in chemistry. Besides simple hydrocarbon alkenes and alkynes, numerous functionalized derivatives are also known and widely employed in organic chemistry. Despite the ubiquity and prominance of both I^III species and olefins and acetylenes, the combination of these two types of functional groups in a single molecular unit, namely compounds with polyvalent iodine and at least one alkyne or olefin residue, was unknown until recently. The successful preparations of simple alkynyl- and alkenyl-(phenyl)iodonium species during the 1980s has resulted in a renaissance in both acetylene and I^III chemistry. These alkynyliodonium compounds readily undergo nucleophilic substitution on the alkyne moiety (S_N-A reactions) which are difficult with other substrates. The application of a wide variety of nucleophiles in this reaction resulted in diverse functionalized alkynes including previously unknown acetylenic carboxylates, sulfonates, and phosphates. These are excellent substrates for cycloaddition reactions as well as numerous other interesting chemical transformations.     

Induced Fit of C2H2 in a Flexible MOF Through Cooperative Action of Open Metal Sites

Porous materials that can undergo pore‐structure adjustment to better accommodate specific molecules are ideal for separation and purification. Here, we report a stable microporous metal‐organic framework, JNU‐1, featuring one‐dimensional diamond‐shaped channels with a high density of open metal sites arranged on the surface for the cooperative binding of acetylene. Together with its framework flexibility and appropriate pore geometry, JNU‐1 exhibits an induced‐fit behavior for acetylene. The specific binding sites and continuous framework adaptation upon increased acetylene pressure are validated by molecular modeling and in situ X‐ray diffraction study. This unique induced‐fit behavior endows JNU‐1 with an unprecedented increase in the acetylene binding affinity (adsorption enthalpy: up to 47.6 kJ mol^?1 at ca. 2.0 mmol g^?1 loading).     

Importance of O(3P) atoms and OH radicals in hydrocarbon oxidation during the nonthermal plasma treatment of diesel exhaust inferred using relative‐rate methods

The consumption of acetylene and propene during passage of simulated diesel exhaust through a nonthermal plasma at 453 K and atmospheric pressure was studied using experimental and computational techniques. Experimental observations of the relative decay rates of acetylene and propene and computer modeling of the chemical and physical processes in the plasma suggest that O(³P) atoms and, to a lesser extent, OH radicals are the dominant species responsible for initiating hydrocarbon oxidation in this system. Results are discussed in terms of the gas‐phase chemistry occurring during the nonthermal plasma treatment of diesel exhaust. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 231–238, 2003     

高压化学

高压化学在现代科学中占有重要的地位,并在过去二十几年中取得了快速的发展。本文简要介绍了高压化学及高压化学研究领域在诸多方面的研究进展,其中包括高压无机化学和高压有机化学,以及高压在化学合成和化学过程研究中的应用,展示了高压化学的研究现状及其在许多方面的应用前景。     

Arenesulfonyl Fluoride Synthesis via Copper‐free Sandmeyer‐type Fluorosulfonylation of Arenediazonium Salts

The limited availability of highly valuable arenesulfonyl fluorides seriously hinders their further application in many research fields including medicinal chemistry and chemical biological, organic synthesis, polymer preparation, etc. We report herein a mild and efficient copper‐free Sandmeyer‐type fluorosulfonylation reaction of various arenediazonium salts to prepare valuable arenesulfonyl fluorides using K₂S₂O₅ as both a reductant and a practical sulfonyl source in combination with N‐fluorobenzenesulfonimide as an effective fluorine source. This methodology provides an attractive route to diverse important arenesulfonyl fluorides given the overall practicality and scope.     

Effect of pressure on the growth of boron and nitrogen doped HFCVD diamond films on WC–Co substrate

Boron and nitrogen compounds are added in the acetone/hydrogen gas mixture to deposit hot filament chemical vapor deposition (HFCVD) diamond films on the cobalt cemented tungsten carbide (WC–Co) substrate under the pressure of 1–4 kPa. The as‐deposited diamond films are characterized by field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), X‐ray diffraction (XRD) spectroscopy and Raman spectroscopy. The results reveal that the surface morphology, growth rate, structure and quality of the diamond films vary with the pressure and the type of the impurity addition. The diamond grains tend to develop into the nanometer scale with the decrease of the pressure. However, adding of boron or nitrogen impurities in the gas mixture will weaken the nanocrystallization effect by reducing the carbon supersaturation. Density functional theory (DFT) calculations indicate that co‐adsorption of B and N containing radicals can favor the adsorption of CH₃ on diamond (100) surface. Thus, at low pressure of 1 kPa, large grained cubic (100) facet diamond rather than typical nanometer diamond is produced for B–N co‐addition gas mixture. The present results appear to be useful to efficiently synthesize high quality doped diamonds with desirable properties for mechanical application. Copyright © 2015 John Wiley & Sons, Ltd.