Reductive debenzylation of hexabenzylhexaazaisowurtzitane — the key step of the synthesis of polycyclic nitramine hexanitrohexaazaisowurtzitane

Main features of the reductive debenzylation of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazaisowurtzitane were studied. This process is the key step of the synthesis of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0^3,11.0^5,9]dodecane (hexanitrohexaazaisowurtzitane, CL-20), a compound with unique energetic and explosive characteristics. The use of the latter is restricted so far by the high cost of the two-step process of debenzylation during which the compound is rapidly deactivated. The expensive Pd/C catalyst is deactivated in the first step of the process, which limits the use of this polycyclic nitramine. The influence of the solvent nature; loadings of the reactants, catalyst, and cocatalyst; the hydrogen pressure and reaction temperature on the general features of the process and the yield of the target precursor of CL-20 was studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2290–2295, December, 2007.     

Structure of a bimolecular crystal of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane and methoxy-<Emphasis Type="Italic">NNO</Emphasis>-azoxymethane

The crystal structure of the bimolecular crystal of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and methoxy-NNO-azoxymethane (МАМ) (1:2) is studied. The CL-20 molecules adopt a ζ-conformation. The crystal structure is formed by layers of CL-20 and МАМ molecules, between which there are shortened NO^δ–?N^δ+O contacts of the neighboring CL-20 and МАМ molecules.     

Ni- and Pd-based homogeneous catalyst systems for direct oxygenation of C(sp3)-H groups

Developing catalytic approaches to selective activation and functionalization of C–H bonds in hydrocarbons and complex organic molecules has been considered as a challenging goal. Recently, significant efforts have been aimed at the search for efficient nickel- and palladium-based catalyst systems, capable of conducting direct aliphatic C–H oxygenation with high and predictable chemoselectivity and regioselectivity. The present review focuses on the advances in homogeneous oxidation of hydrocarbon C(sp³)–H groups, catalyzed by nickel and palladium complexes, and covers the publications of the past 15 years. Correlations between the structure of the metal-based catalyst, steric and electronic properties of the ligands, catalytic conditions, and the catalytic reactivity (efficiency, chemoselectivity, and regioselectivity) are discussed.     

A new synthesis of 25-hydroxycholesterol

A simple (η³-allyl)palladium-based synthesis of 25-hydroxycholesterol is described using a dimetallated coupling reagent.     

New catalytic systems for oxidative carbonylation of acetylene to maleic anhydride

A classification of polyfunctional catalytic systems based on discrimination of the main component (the catalyst participating in all stages of the formation of the product of catalytic reaction) and elucidating the functions of additional components of a catalytic system is suggested. The role of additional components in a number of new palladium-based catalytic systems used in the synthesis of maleic anhydride by oxidative carbonylation of acetylene was studied. It was established that the functions of Co and Fe phthalocyanine complexes (PcCo and Pc^*Fe, respectively) in the mechanism of the process are different. Translated fromIzvestia Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1899–1905, October, 1999.     

Pd immobilized on thiol-modified magnetic nanoparticles: A complete magnetically recoverable and highly active catalyst for hydrogenation reactions

A palladium-based catalyst supported on thiol-modified superparamagnetic nanoparticles was successfully prepared by co-precipitation method. These magnetic nanomaterials were characterized by elemental analysis (EA), inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fourier transform-infrared (FT-IR), thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM). The conversions of various aromatic nitro and unsaturated compounds can receive a really high yield with the existence of magnetic nanomaterials. The turn-over frequency (TOF) can be 66.46 h⁻¹ in ethanol under a H₂ atmosphere at room temperature. In this paper, the conversions of aromatic nitro bearing a variety of substituents were 93.56–100%, moreover, the catalyst afforded over 90% yield in the reducing unsaturated compounds. Another advantage is that the magnetite nanoparticles modified by thiol group can be separated just through the external magnetic force and can be reused atleast ten times without any significant loss in activity.     

Hydrogen Peroxide Solvates of 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane

Two polymorphic hydrogen peroxide solvates of 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20; wurtzitane is an alternative name to iceane) were obtained using hydrated α‐CL‐20 as a guide. These novel H₂O₂ solvates have high crystallographic densities (1.96 and 2.03 g cm^?3, respectively), high predicted detonation velocities/pressures (with one solvate performing better than ?‐CL‐20), and a sensitivity similar to that of ?‐CL‐20. The use of hydrated materials as a guide will be important in the development of other energetic materials with hydrogen peroxide. These solvates represent an area of energetic materials that has yet to be explored.     

Pentanitro- and pentanitronitroso-2,4,6,8,10,12-hexaazaisowurtzitanes

Reduction of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane with a sub-stoichiometric amount of SnCl₂ afforded a mixture of isomeric 2,4,6,8,10- and 2,4,6,8,12-pentanitro-2,4,6,8,10,12-hexaazaisowurtzitanes, their ratio depending on the solvent used. Treatment of these compounds with NOBF₄ gave rise to isomeric pentanitronitroso-2,4,6,8,10,12-hexaazaisowurtzitanes, which can be transformed into the starting NH products by treating with HCl.     

Catalytic hydroallylation of norbornadiene with allyl formate

Norbornadiene (NBD) reacts with allyl esters All—OC(O)R (R = Me, Bu^t, Ph, CCl₃, CF₃) in acetonitrile solutions of palladium(0) complexes to give a mixture of four isomeric nontraditional allylation products and the corresponding carboxylic acids. Under similar conditions, the reaction of NBD with allyl formate in solutions of Pd⁰ and Pd^II complexes occurs selectively, resulting in the product of addition of the allyl fragment and the H atom to an NBD double bond, 5-allylbicyclo[2.2.1]hept-2-ene, and CO₂. The hydroallylation of NBD is accompanied by catalytic addition of formic and acetic acids to one double bond of the diene to give bicyclo[2.2.1]hept-2-en-5-ol and nortricyclan-3-ol acetates and formates. Unlike most known palladium-based catalyst systems, these complexes exhibit catalytic activity also in the absence of phosphines. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 309–313, February, 2007.     

DFT study on the structure and detonation properties of amino,methyl, nitro,and nitroso substituted 3,4,5-trinitropyrazole-2-oxides: New high energy materials

The structure, band gap, thermodynamic properties and detonation properties of methyl, amino, nitro, and nitroso substituted 3,4,5-trinitropyrazole-2-oxides are explored using density functional theory at the B3LYP/aug-cc-pVDZ level. It is found that the NH₂ or CH₃ group substitution for the acidic proton at the N4 position of trinitropyrazole-2-oxide (P20) decreases the heat of detonation and crystal density. The density (2.20–2.50 g/cm³), detonation velocity (10.20–10.92 km/s), and detonation pressure (52.30–59.84 GPa) of the title compounds are higher compared with 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), and octanitrocubane (ONC).     

Debenzylation of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.03,11.05,9]dodecane

The debenzylation of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazatetra-cyclo[5.5.0.0^3,11.0^5,9]dodecane by catalytic hydrogenolysis in a mixture of HCOOH with other RCOOH (R = Me, Et, Prⁱ) is accompanied by the N-formylation of the liberated secondary amino groups. The alkaline hydrolysis of the obtained products makes it possible to remove the formyl groups with the retention of the acetyl groups.     

Oxidation of N-benzyl groups

The oxidative reactivity of 2,6,8,12-tetraacetyl-4,10-dibenzy1-2,4,6,8,10,12-hexaazatetracydot[5,5.0,05.9.03.11] dodecane (3) in several conditions was studied.It was found that the N-benzyl groups in compound 3 could be oxidized to benzoyi groups byCr(Ⅵ) reagents,and could be removed by cerium ammonium nitrate (CAN),meanwhile nitroamine products were given.     

Star‐like polyfluorenes based on 2,4,6,8, 10,12‐hexabenzyl‐2,4,6,8,10,12‐hexaazaisowurtzitane caged‐core: toward non‐aggregating,blue‐light‐emitting polymers

Multi‐functionality compound 2,4,6,8,10,12‐hexa(p‐bromo)‐benzyl‐2,4,6,8,10,12‐hexaazaiso‐wurtzitane (Br‐HBIW) was synthesized and used for the core of star‐like polymers. Star‐like polyfluorene based on 2,4,6,8,10,12‐hexabenzyl‐2,4,6,8,10,12‐hexaazaisowurtzitane (HBIW) caged‐core was synthesized by Suzuki coupling method. The comparative studies between the star‐like polyfluorene and the linear polyfluorene based on UV–Vis and photoluminescence (PL) spectra revealed that the bulky HBIW cage could reduce the chain aggregation and π–π interaction, so brought about improved PL quantum efficiency and annealing PL stability. Such results could be owed to the successful suppression of excimers formation, which originated from the incorporation of the HBIW cage and star‐like architecture. Copyright © 2009 John Wiley & Sons, Ltd.     

Immobilized palladium on surface-modified Fe3O4/SiO2 nanoparticles: as a magnetically separable and stable recyclable high-performance catalyst for Suzuki and Heck cross-coupling reactions

A palladium-based catalyst (Fe₃O₄/SiO₂/HPG–OPPh₂–PNP) supported on chlorodiphenylphosphine-functionalized magnetic nanoparticles was successfully prepared from Fe₃O₄/SiO₂ with sequential attachment of glycerol and chlorodiphenylphosphine, followed by treatment of an ethanolic solution of palladium chloride with hydrazine. The as-prepared catalyst was characterized by ICP-AES, FTIR, XRD, SEM, and TEM. The Fe₃O₄/SiO₂/HPG–OPPh₂–PNP was found as a magnetically separable and highly active catalyst for Suzuki coupling reactions of aryl iodides, bromides, and chlorides as well as Heck reactions of aryl iodides and bromides. Under appropriate conditions, all reactions afforded the desired products in moderate to excellent yields. Moreover, this catalyst can be easily recovered by using a magnetic field and directly reused for at least six cycles without significant loss of its activity.     

Thermal study of HNIW(CL-20) and mixtures containing aluminum powder

The thermal behavior of the energetic material 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-tetracyclo-[5.5.0.0^5,9.0^3,11]-dodecane (HNIW or CL-20) and its mixtures with aluminum under linear temperature control condition and adiabatic condition were investigated by DSC-TG-MS-FT-IR and ARC. Two different particle sizes of aluminum powder (10 μm and 50 nm) were added into CL-20. The influence of particle size on the thermal behavior of CL-20 was studied by using of these apparatuses. The enthalpies of reaction and onset temperatures were determined for various heating rates. The kinetic parameters were found according to Kissinger method, Ozawa method, and Friedman method based on DSC data. The gaseous products from the decomposition of CL-20 and its mixtures were determined by simultaneous MS-FT-IR experiments. ARC measurements were performed to investigate the thermal stability of the samples. The onset temperature, adiabatic temperature rise, self-heat rate, time to maximum rate, and pressure–temperature profile were found from the data measured by ARC. Based on these results, the catalytic effect of aluminum powder was studied.     

Structured Catalysts Prepared by Electroless Plating Technique onto a Metal Substrate, for a Wall-Type Hydrogen Production System

This article reviews our works on the structured catalysts for a wall-type hydrogen production system including methanol steam reforming (MSR), CO shift reaction (CO SR) and methanol decomposition (MD). The structured catalysts were copper-based, palladium-based and nickel-based catalysts. Such a series of structured catalysts were prepared by the electroless plating technique that is a novel method for preparing a structured type catalyst onto a metal-substrate. The copper-based catalyst exhibited high performance for MSR and CO SR, the palladium-based catalyst high for MSR, and the nickel-based catalyst high for MD. The catalytic properties of these catalysts were affected by the difference of the plating condition and the pretreatment condition prior to the reaction. In the copper-based catalyst, the reforming and shift activities were enhanced by the oxidation treatment. One of the factors of such activity enhancement by the oxidation was thought to be in close proximity existence of copper and zinc atoms. A lot of monodentate-type formate species having high reactivity was formed on the oxidized catalyst, which would be correlated to the activity enhancement. In the palladium-based catalyst, the reforming activity was improved by the continuous reduction treatment followed by the oxidation. Such continuous pretreatment formed the PdZn alloy species thought to be a reforming site in the surface layer. The decomposition performance of the nickel-based catalyst depended on the ratio of the crystallite size of nickel particles to that of aluminum particles. The electronic influence of zinc and phosphorous components incorporated in the plated layer contributed to the improvement of the selectivity of product.     

Recent Advances in Transition Metal-Based Catalysts for Ethylene Copolymerization with Polar Comonomer

The synthesis of polar functionalized polyolefin (PFP) offers improvement in mixing properties, polymer surface, and rheological properties with the potential of upgraded polyolefins for modern and ingenious applications. The synthesis of PFP from metal-based catalyzed olefin (non-polar in nature) copolymerization with polar comonomers embodies energy-efficient, atom-efficient, and apparently an upfront methodology. Despite their outstanding success during conventional polymerization of olefin, 3^rd and 4^th group (early transition metal)-based catalysts, owing to their electrophilic nature, face challenges mainly due to Lewis basic sites of the polar monomers. On the contrary, late transition metal-based catalysts have also made progress, in recent years, for PFP synthesis. The recent past has also witnessed several advancements in the development of dominating palladium-based catalysts while their lower resistance towards ligand functional groups has limited the practical application of abundant and cheaper nickel-based catalysts. However, the relentless efforts of the scientific community, during the past half-decade, have indicated rigorous progress in the development of nickel-based catalysts for PFP synthesis. In this review, we have abridged the recent research trends in both early as well as late transition metal-based catalyst development. Furthermore, we have highlighted the role of transition metal-based catalysts in influencing the polymer properties.     

Structure and properties of cocrystals of trinitrotoluene and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane

Crystals containing 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane and trinitrotoluene molecules in a 1: 1 ratio were obtained. The crystal structure was determined, and DSC thermograms, thermal stability, and the standard enthalpy of formation were investigated. An analysis of the crystal structure shows that interactions between the oxygen and nitrogen atoms of the nitro groups ON=O…NO₂ of adjacent molecules are among the structure-forming intermolecular interactions in the crystals of polynitroamine compounds.     

Determination of coordination modes and estimation of the 31P-31P distances in heterogeneous catalyst by solid state double quantum filtered 31P NMR spectroscopy

To overcome the separation difficulty of the palladium-based homogeneous catalyst, the palladium complex can be anchored on various supports such as silica. However, it is difficult to determine the amounts of the two coordination modes of the Pd nucleus, that is, Pd coordinates with one phosphorus atom and Pd coordinates with two phosphorus atoms. Here a (31)P double-quantum filtered (DQ-filtered) method in solid-state NMR is introduced for the palladium-based heterogenous catalyst system. With the DQ-filtered method, we can not only determine the amounts of the two different kinds of palladium coordination modes, we can also estimate the interatomic distance of two (31)P nuclei bonded to a palladium nucleus. With the help of this method, we can quickly estimate interatomic distances in our designed system and accurately re-design the palladium system to accommodate either one (31)P or two (31)P.     

Nitration of benzyl derivatives of acetylated hexaazaisowurtzitane

Nitration of N-benzylated 2,4,6,8,10,12-hexaazaisowurtzitane derivatives occurs selectively at para-positions of the benzyl groups. The best reagent for this reaction is ammonium nitrate in sulfuric acid.