Gas-free Conditions Research Articles

CN-Doped Cobalt Oxide Composite: An Economic and Reusable Catalyst with Multitasking Catalytic Capability for Alkyne and Nitrile Hydrations and Nitro Reductions

AbstractA heterogeneous CoOCN composite was synthesized via a one-pot reaction of [Co(NO3)2] and urea at 500 °C in a muffle furnace. The composite was fully characterized by FTIR, Raman, powder XRD, and XPS techniques. The catalyst was found to be efficient for the hydrations of aryl alkynes and nitriles under aerobic conditions. In addition, the catalyst exhibits high catalytic performance for the reduction of nitroarenes under inert gas-free conditions. This multitasking CoOCN composite was found to be highly suitable for all derivatives of nitrobenzene, alkynes, and nitriles because good to excellent yields were obtained. The catalyst was recovered quantitatively from the reaction mixture by simple filtration and consequently reused for seven consecutive cycles in all reactions without significant loss of catalytic activity. Hence, the synthesized CN-doped CoOCN composite worked as a multitasking catalyst for various value-added organic transformations, and it is highly economical and reusable for up to seven catalytic cycles without any activation, with even the last cycle producing reasonable yields of up to 48–50%.

Gas-free alkoxycarbonylation of aryl iodides in a phosphonium-based deep eutectic solvent with Mo(CO)6 as a solid CO source.

Pd-catalyzed alkoxycarbonylation of aryl iodides has been explored, for the first time, in phosphonium-based deep eutectic solvents under gas-free conditions, by using Mo(CO)6 as the CO source. The method allows the preparation of ethylene glycol and glycerol esters in high yields (up to 99%), short reaction times and under mild reaction conditions with a very low catalyst loading (0.5 mol%).

Palladium-catalyzed Heck-carbonylation of alkene-tethered carbamoyl chlorides with aryl formates.

We report a palladium-catalyzed Heck-carbonylation of alkene-tethered carbamoyl chlorides by utilizing aryl formates as convenient CO surrogates. One C-O and two C-C bonds are constructed to give diversiform esterified oxindoles/γ-lactams bearing an all-carbon quaternary stereocenter under gas-free conditions. This transformation features a wide substrate scope and good functional group tolerance and can be easily applied to late-stage functionalization.

Dimensionality Control of Inorganic and Hybrid Perovskite Nanocrystals by Reaction Temperature: From No-Confinement to 3D and 1D Quantum Confinement.

This work focuses on the systematic investigation of the shape, size, and composition‐controlled synthesis of perovskite nanocrystals (NCs) under inert gas‐free conditions and using pre‐synthesized precursor stock solutions. In the case of CsPbBr3 NCs, we find that the lowering of reaction temperature from ∼175 to 100 °C initially leads to a change of morphology from bulk‐like 3D nanocubes to 0D nanocubes with 3D‐quantum confinement, while at temperatures below 100 °C the reaction yields 2D nanoplatelets (NPls) with 1D‐quantum confinement. However, to our surprise, at higher temperatures (∼215 °C), the reaction yields CsPbBr3 hexapod NCs, which have been rarely reported. The synthesis is scalable, and their halide composition is tunable by simply using different combinations of precursor solutions. The versatility of the synthesis is demonstrated by applying it to relatively less explored shape‐controlled synthesis of FAPbBr3 NCs. Despite the synthesis carried out in the air, both the inorganic and hybrid perovskite NCs exhibit nearly‐narrow emission without applying any size‐selective separation, and it is precisely tunable by controlling the reaction temperature.

Palladium nanoparticles on amino-modified silica-catalyzed C–C bond formation with carbonyl insertion

A practical and heterogeneously catalyzed Stille, homo-coupling, and Suzuki carbonylation reaction has been reported using Pd nanoparticles supported on amino-vinyl silica-functionalized magnetic carbon nanotube (CNT@Fe3O4@SiO2-Pd) for the efficient synthesis of symmetrical and unsymmetrical diaryl ketones from aryl iodides. A wide variety of symmetrical and unsymmetrical diaryl ketones were obtained in high yields under CO gas-free conditions using Mo(CO)6 as an efficient carbonyl source. Considering the atom economy of Ph3SnCl, less than an equimolar amount can be applied in Stille transformation, which is of great importance due to the toxicity of organotin derivatives. Moreover, no phosphine ligand and external reducing agent were necessary in these coupling carbonylation reactions. This heterogeneous Pd catalyst offers high activity with very low palladium leaching. Finally, the catalyst can be reused and recycled for six steps without loss in activity, exhibiting good example of sustainable methodology.

A Magnetically Recyclable Palladium-Catalyzed Formylation of Aryl Iodides with Formic Acid as CO Source: A Practical Access to Aromatic Aldehydes

AbstractA magnetically recyclable palladium-catalyzed formylation of aryl iodides under CO gas-free conditions has been developed by using a bidentate phosphine ligand-modified magnetic nanoparticles-anchored­ palladium(II) complex [2P-Fe3O4@SiO2-Pd(OAc)2] as catalyst, yielding a wide variety of aromatic aldehydes in moderate to excellent yields. Here, formic acid was employed as both the CO source and the hydrogen donor with iodine and PPh3 as the activators. This immobilized palladium catalyst can be obtained via a simple preparative procedure and can be facilely recovered simply by using an external magnetic field, and reused at least 9 times without any apparent loss of catalytic activity.

Tandem Synthesis of 2-Carboxybenzofurans via Sequential Cu-Catalyzed C-O Coupling and Mo(CO)6-Mediated Carbonylation Reactions.

A modular tandem synthesis of 2-carboxybenzofurans from 2-gem-dibromovinylphenols has been established based on a sequence of Cu-catalyzed intramolecular C-O coupling and Mo(CO)6-mediated intermolecular carbonylation reactions. This protocol allowed one-step access to a broad variety of functionalized benzofuran-2-carboxylic acids, esters, and amides in good to excellent yields under Pd- and CO gas-free conditions.

Recyclable heterogeneous palladium-catalyzed carbonylative Sonogashira coupling under CO gas-free conditions

A convenient, efficient and practical heterogeneous palladium-catalyzed carbonylative Sonogashira coupling of aryl iodides with terminal alkynes under CO gas-free conditions has been developed by using an MCM-41-supported bidentate phosphine palladium acetate complex as catalyst. Here, formic acid was used as the CO source with dicyclohexylcarbodiimide (DCC) as the activator and a wide variety of alkynyl ketones were generated in moderate to high yields. This heterogeneous palladium catalyst can be easily recovered via a simple filtration process and recycled up to 8 times without apparent loss of activity.

Carbonylative Transformation of Allylarenes with CO Surrogates: Tunable Synthesis of 4-Arylbutanoic Acids, 2-Arylbutanoic Acids, and 4-Arylbutanals.

In this Communication, procedures for the selective synthesis of 4-arylbutanoic acids, 2-arylbutanoic acids, and 4-arylbutanals from the same allylbenzenes have been developed. With formic acid or TFBen as the CO surrogate, reactions proceed selectively and effectively under carbon monoxide gas-free conditions.

Palladium-Catalyzed Carbonylative Synthesis of Isoindolinones from Benzylamines with TFBen as the CO Source.

A palladium-catalyzed C-H carbonylation of benzylamines for the synthesis of isoindolinone scaffolds has been developed. This protocol is conducted under gas-free conditions by using benzene-1,3,5-triyl triformate (TFBen) as a convenient CO surrogate, furnishing a variety of isoindolinone derivatives in moderate to high yields (up to 95%).

Silver(i)-catalysed carboxylative cyclisation of primary propargylic amines in neat water using potassium bicarbonate as a carboxyl source: an environment-friendly synthesis of Z-5-alkylidene-1,3-oxazolidin-2-ones

An environment-friendly synthesis of Z-5-alkylidene-1,3-oxazolidin-2-ones in water under gas-free conditions.

Facile benzofuran synthesis: Palladium-catalyzed carbonylative Suzuki coupling of methyl 2-(2-iodophenoxy)acetates under CO gas-free conditions

A palladium-catalyzed carbonylative Suzuki coupling of methyl 2-(2-iodophenoxy)acetates with arylboronic acids has been developed. The reactions were performed under CO gas-free conditions and the obtained products act as a direct precursor for the synthesis of highly functionalized benzofuran derivatives.

A Convenient Palladium-Catalyzed Carbonylative Suzuki Coupling of Aryl Halides with Formic Acid as the Carbon Monoxide Source.

A practical palladium-catalyzed carbonylative Suzuki coupling of aryl halides under carbon monoxide gas-free conditions has been developed. Here, formic acid was utilized as the carbon monoxide source for the first time with acetic anhydride as the additive. A variety of diarylketones were produced in moderate to excellent yields from the corresponding aryl halides and arylboronic acids.

Pd/C-catalyzed dechlorination of polychlorinated biphenyls under hydrogen gas-free conditions

The simultaneous use of catalytic amount of palladium on carbon (Pd/C) and Mg metal (1.5–2.0 equiv vs. Cl numbers of the substrates) in MeOH achieved the complete dechlorination of a variety of aryl chlorides at room temperature under a nitrogen atmosphere in the absence of hydrogen gas. The present method could be successfully used for the detoxification of PCBs based on the dechlorinaton reaction. Both virgin PCBs, such as Aroclors 1242, 1248 and 1254, and used PCBs as a high-tension capacitor oil, were smoothly dechlorinated into harmless biphenyl without any byproducts within 2h at rt. The distinctive features of this method are convenience and safety due to no needs for the pretreatment of catalyst and Mg and complete degradation of PCBs under mild conditions without hydrogen gas.

Dynamical Models of Terrestrial Planet Formation

We review the problem of the formation of terrestrial planets, with particular emphasis on the interaction of dynamical and geochemical models. The lifetime of gas around stars in the process of formation is limited to a few million years based on astronomical observations, while isotopic dating of meteorites and the Earth-Moon system suggest that perhaps 50-100 million years were required for the assembly of the Earth. Therefore, much of the growth of the terrestrial planets in our own system is presumed to have taken place under largely gas-free conditions, and the physics of terrestrial planet formation is dominated by gravitational interactions and collisions. The earliest phase of terrestrial-planet formation involve the growth of km-sized or larger planetesimals from dust grains, followed by the accumulations of these planetesimals into ∼100 lunar- to Mars-mass bodies that are initially gravitationally isolated from one-another in a swarm of smaller planetesimals, but eventually grow to the point of significantly perturbing one-another. The mutual perturbations between the embryos, combined with gravitational stirring by Jupiter, lead to orbital crossings and collisions that drive the growth to Earth-sized planets on a timescale of 107-108 years. Numerical treatment of this process has focussed on the use of symplectic integrators which can rapidy integrate the thousands of gravitationally-interacting bodies necessary to accurately model planetary growth. While the general nature of the terrestrial planets-their sizes and orbital parameters-seem to be broadly reproduced by the models, there are still some outstanding dynamical issues. One of these is the presence of an embryo-sized body, Mars, in our system in place of the more massive objects that simulations tend to yield. Another is the effect such impacts have on the geochemistry of the growing planets; re-equilibration of isotopic ratios of major elements during giant impacts (for example) must be considered in comparing the predicted compositions of the terrestrial planets with the geochemical data. As the dynamical models become successful in reproducing the essential aspects of our own terrestrial planet system, their utility in predicting the distribution of terrestrial planet systems around other stars, and interpreting observations of such systems, will increase.

Gas-freeing of crude oil tanks – analysis using numerical simulation

Marine gas-freeing is a seldom-examined operation that takes place on board oil tankers ahead of some cargo transitions and tank maintenance/inspection cycles. Since the introduction of inert gas systems (IGS), tanker explosions have been minimised, but the issue of toxic vapours inside the tank still exists. Another issue relating to gas-freeing concerns the actual time required to ensure gas-free conditions; there are no regulatory considerations for the minimum times for gas-freeing, which stands in contrast to regulations concerning other areas on board a vessel.Through the use of modern computational methods, gas-freeing processes have been modelled and simulated in order to determine the progression of gas-freeing with regards to examining the concentration and distribution of vapours inside the tank during the procedure, as well as studying the decrease in total average concentration with regards to forming a simple qualitative model to predict the time required to gas-free given certain initial conditions.

Facile and Efficient Postsynthetic Tritium Labeling Method Catalyzed by Pd/C in HTO

[reaction: see text] We have developed a facile and efficient tritium labeling method using a Pd/C-HTO-H2 system. This method can provide multitritium-labeled compounds in highly diluted HTO under T2 gas-free conditions, and is environmentally benign since purification by silica gel column chromatography is not necessary, which causes a large quantity of radioactive waste such as silica gel and eluent.

Solar wind origin of 36Ar on Venus

A hypothesis is considered in which the 36Ar found on Venus is of solar origin. This possibility is quantitatively discussed within the framework of present theories of planetary accumulation by sweep up of planetesimals under gas-free conditions. Solar wind implantation of 36Ar would take place by irradiation of accumulating material during the first ≈10 5 years of planetary growth, provided that the flux of solar wind was enhanced by a factor of ≈100 at that time. Enrichment of Venus in implanted gas would be a consequence of the irradiated material being initially confined to the innermost edge of the radially opaque circusolar planetesimal disk predicted by these theories. The observed atmospheric data require a Ne/Ar fractionation by a factor of ≈100 during the planetesimal stage. It is also necessary that there be very little mixing of irradiated planetesimals from the inner edge of disk to the distance (≈1 AU) at which the Earth formed. The hypothesis can be tested by measurement of the abundance of Kr and Xe in the Venus atmosphere. Venera data indicate a terrestrial 36Ar/Kr ratio, in disagreement with the solar wind hypothesis. In contrast, the Pioneer experiments find a lower limit to this ratio, well above the terrestrial value, that is compatible with the hypothesis. These experiments also show that Venus' 36Ar/Xe ratio does not correspond to the so-called “planetary” trapped inert gas composition. The inert of Venus could be related to result of admixture of gas with solar composition. The inert gas on Venus could be related to that found in enstatite chondrites.

The Magnetic Behavior of Nickel and Iron Films Condensed in Vacuum upon Various Metal Backings

The magnetic nature of evaporated iron and nickel films deposited on various kinds of backings was investigated to determine the effect of the two-dimensional strain which the backing must impose upon the film due to differential thermal contraction. The films were, of necessity, deposited at elevated temperatures and measured at room temperature. The temperature of deposit was varied. Nickel samples deposited on backings which place the film under tension were found to be extremely hard, magnetically, while compression made the film comparatively soft. The magnetic intensity of iron samples in general was not changed markedly by these stresses. All the samples were harder than bulk metal. The method used to describe the results shows that films deposited at higher temperatures are more like annealed bulk metal, rather than less so as others have concluded. Extreme precautions were taken to deposit the films under gas free conditions so that it was possible to be sure that the abnormal hardness of films deposited at ordinary temperatures was due to the different manner in which the metal condenses and not due to the presence of gas. A novel arrangement of the magnetizing coil of a sensitive astatic magnetometer used for the magnetic measurements is described.