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A simple and practical procedure for the selective preparation of 3H-indol-3-one and indolo[1,2-c]quinazoline derivatives through copper-catalyzed aerobic oxygenation and intramolecular cyclization reactions of 2-(2-amidoaryl)-1H-indoles in the presence of acid has been disclosed. Interestingly, the reaction outcomes are exclusively dependent on the reaction medium employed. With DMF as the solvent, the amide moiety of indole substrates could act as an auxiliary to enable the indole's oxygenation reaction with molecular oxygen from air as the oxidant to give 3H-indol-3-one derivatives in a highly selective manner. On the other hand, when the reactions were performed in 1,4-dioxane, the amide moiety switched to participate in an intramolecular indolyl N1-cyclization to afford indolo[1,2-c]quinazolines as the predominating products. [ABSTRACT FROM AUTHOR]

A new one-pot strategy for the synthesis of quinoxalin-2-ones from the tandem nitrosation/cyclization reaction of N-aryl cyanoacetamides with tert-butyl nitrite has been developed. The dehydrogenative N-incorporation is achieved through a sequence of nitrosation, tautomerization, and cyclization, affording quinoxalin-2-ones in moderate to good yields with good functional group tolerance. [ABSTRACT FROM AUTHOR]

A new cascade three-component haloazidation of benzene-tethered 1,7-enynes for the formation of biologically interesting azidylated 3,4-dihydroquinolin-2(1H)-ones has been achieved under mild and metal-free conditions using TMSN3 as a N3 source and NIS (or NBS or NCS) as a halogen source. The reaction pathway involves in situ-generated azidyl radical-triggered a,β-conjugated addition/6-exo-dig cyclization/radical coupling sequence, resulting in successive multiple bond-forming events, including carbon-nitrogen, carbon-carbon, and carbon-halogen bonds to rapidly construct complex heterocyclic molecules. Furthermore, the resulting products would be useful building blocks in the discovery of lead compounds and other biologically interesting N3-containing heterocycles. [ABSTRACT FROM AUTHOR]

A new cascade three-component haloazidation of benzene-tethered 1,7-enynes for the formation of biologically interesting azidylated 3,4-dihydroquinolin-2(1H)-ones has been achieved under mild and metal-free conditions using TMSN3 as a N3 source and NIS (or NBS or NCS) as a halogen source. The reaction pathway involves in situ-generated azidyl radical-triggered α,β-conjugated addition/6-exo-dig cyclization/radical coupling sequence, resulting in successive multiple bond-forming events, including carbon-nitrogen, carbon-carbon, and carbon-halogen bonds to rapidly construct complex heterocyclic molecules. Furthermore, the resulting products would be useful building blocks in the discovery of lead compounds and other biologically interesting N3-containing heterocycles. [ABSTRACT FROM AUTHOR]

Three representative BINOL derivatives were examined for their chiral recognitions with D- and L-t-Boc-amino acid anions: an open system 1, which bears two urea groups and two pyrene groups; a dosed ring system 2, which bears two urea groups with a closed ring system; and a dimeric system 3, which bears two benzylic amine groups and two pyrene groups. Dimeric system 3 displayed a ΔID/ΔIL of 12.95 for t-Boc-alanine. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were performed to find comprehensive relationships between the structures and performance of a series of highly energetic cyclic nitramines. The isodesmic reaction method was employed to estimate the heat of formation. The detonation properties were evaluated by using the Kamlet-Jacobs equations based on the theoretical densities and HOFs. Results indicate the N-NO2 group and aza N atom are effective substituents for enhancing the detonation performance. All cyclic nitramines except C11 and C21 exhibit better detonation performance than HMX. The decomposition mechanism and thermal stability of these cyclic nitramines were analyzed via the bond dissociation energies. For most of these nitramines, the homolysis of N-NO2 is the initial step in the thermolysis, and the species with the bridged N-N bond are more sensitive than others. Considering the detonation performance and thermal stability, twelve derivatives may be the promising candidates of high energy density materials (HEDMs). The results of this study may provide basic information for the further study of this kind of compounds and molecular design of novel HEDMs. [ABSTRACT FROM AUTHOR]

In this work, the properties of the synthesized high-nitrogen compounds 4,4',6,6'-tetra(azido)azo-1,3,5-triazine (TAAT) and 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT), and a set of designed bridged triazines with similar bridges were studied theoretically to facilitate further developments for the molecules of interests. The gas-phase heats of formation were predicted based on the isodesmic reactions by using the DFT-B3LYP/AUG-cc-PVDZ method. The estimates of the condensed-phase heats of formation and heats of sublimation were estimated in the framework of the Politzer approach. Calculation results show that the method gives a good estimation for enthalpies, in comparison with available experimental data for TAAT and TAHT. The crystal density has been computed using molecular packing calculations. The calculated detonation velocities and detonation pressures indicate that -NF2, -NO2, -N-N-, and -N-N(O)- groups are effective structural units for improving the detonation performance of the bridged triazines. The synthesized TAAT and TAHT are not preferred energetic materials due to their inferior detonation performance. The p→π conjugation effect between the triazine rings and bridges makes the molecule stable as a whole. The electrostatic behavior of the bridged triazines is characterized by an anomalous surface potential imbalance when incorporating the strongly electron-withdrawing -NF2 and -NO2 groups into the molecule. An analysis of the bond dissociation energies shows that all these derivatives have good thermal stability over RDX and HMX, and the -NH-NH- bridge is more helpful for improving the stability than -N-N(O)- and -N-N- bridges. Considering the detonation performance and thermal stability, three bridged triazines may be considered as the potential candidates of high-energy density materials (HEDMs). [ABSTRACT FROM AUTHOR]

Studies have suggested that octanitrocubane (ONC) is one of the most powerful non- nuclear high energy density material (HEDM) currently known. 2,4,6,8-Tetranitro- 1,3,5,7-tetraazacubane (TNTAC) studied in this work may also be a novel HEDM due to its high nitrogen content and crystal density. Density functional theory and molecular mechanics methods have been employed to study the crystal structure, IR spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heat of formation, detonation performance, and pyrolysis mechanism of TNTAC. The TNTAC has a predicted density of about 2.12 g/cm³, and its detonation velocity (10.42 km/s) and detonation pressure (52.82 GPa) are higher than that of ONC. The crystalline packing is P212121, and the corresponding cell parameters are Z = 4, a = 8.87 Å, b = 8.87 Å, and c = 11.47 Å. Both the density of states of the predicted crystal and the bond dissociation energy of the molecule in gas phase show that the cage C-N bond is the trigger bond during thermolysis. The activation energy of the pyrolysis initiation reaction obtained from the B3LYP/6-311++G(2df,2p) level is 125.98 kJ/mol, which indicates that TNTAC meets the thermal stability request as an exploitable HEDM. [ABSTRACT FROM AUTHOR]

An efficient synthetic procedure for the preparation of fused 2,3-dihydrofuran derivatives was developed with the assistance of pyridinium ylide. A sequential one-pot, two-step tandem reaction starting from pyridine, aromatic aldehyde, dimedone, or 4-hydroxycoumarin and α-phenacyl bromide or p-nitro- benzyl bromide with triethylamine as catalyst proceeded smoothly in acetonitrile. ¹H NMR spectroscopy and single-crystal analysis demonstrated that the obtained 2,3-dihydrofurans are trans isomers. [ABSTRACT FROM AUTHOR]

Polysubstituted pyrido[1,2-α]benzimidazole derivatives are efficiently produced in moderate yields in a novel one-pot, four-component reaction from pyridine or 3-picoline, chloroacetonitrile, malononitrile, and aromatic aldehyde in refluxing acetonitrile. The mechanism of this novel reaction was believed involving the formation of polysubstituted benzenes with subsequent substitution and annulation reaction of pyridine. All pyrido[1,2-α]benzimidazoles, polysubstituted benzenes, polysubstituted indoles, and some key reaction intermediates are characterized by 1H and 13C NMR, MS, IR spectra, and elemental analysis as well as X-ray crystallography. [ABSTRACT FROM AUTHOR]

Eighteen structures of new organic alkalides (Mn6adz)M‘-(M, M‘ Li, Na, K; n2, 3) with the alkali-metal cation Mlying near the center of the adz cage and the alkali-metal anion M‘-located outside are obtained with all real frequencies. They exhibit very large static first hyperpolarizabilities (0) up to 3.2 × 105au, which exceeds the record value of 01.7 × 105au for nonlinear optical compounds Chem.Eur. J.1997, 3, 1091. All potassides (Mn6adz)K-(M Li, Na, K; n2, 3) have considerably large 0values (1.6 × 105−3.2 × 105au) much larger than the 0value (3.6 × 104au) of the previously designed cuplike alkalide Li(calix4pyrrole)K-J. Am. Chem. Soc. 2006, 128, 1072. This shows that the 26adz and 36adz cage complexants are preferable to cuplike calix4pyrrole complexant in enhancing the first hyperpolarizability. The effect of cage size of the complexant on the first hyperpolarizability is also presented here:  in most cases, the smaller cage complexant corresponds to the larger 0value. Moreover, the crucial role by the alkali-metal anion in the large first hyperpolarizability of these alkalides is revealed. These results may provide new means for designing high-performance nonlinear optical materials. [ABSTRACT FROM AUTHOR]

A feasible nucleophilic trifluoromethylating protocol has been developed using trifluoroacetaldehyde hydrate as an atom-economical trifluoromethyl source. The reaction was found to be applicable to the nucleophilic trifluoromethylation of a broad spectrum of carbonyl compounds with satisfactory yields in general. DFT calculations have been performed to provide mechanistic insight into the present and related reactions employing 2,2,2-trifluoro-1-methoxyethanol and hexafluoroacetone hydrate. [ABSTRACT FROM AUTHOR]

Polynitro cage compound 4-trinitroethyl-2,6,8,10,12-pentanitrohexaazaisowurtzitane has the same framework with but higher stability than CL-20 and is a potential new high energy density compound (HEDC). In this paper, the B3LYP/6-31G(d,p) method of density functional theory (DFT) has been used to study its heat of formation, IR spectrum, and thermodynamic properties. The stability of the compound was evaluated by the bond dissociation energies. The calculated results show that the first step of pyrolysis is the rupture of the N--NO2 bond in the side chain and verify the experimental observation that the title compound has better stability than CL-20. The crystal structure obtained by molecular mechanics belongs to the P212121 space group, with lattice parameters a = 12.59 Å, b = 10.52 Å, c = 12.89 Å, Z = 4, and p = 2.165 g ⋅ cm-3. Both the detonation velocity of 9.767 km ⋅ s-1 and the detonation pressure of 45.191 GPa estimated using the Kamlet-Jacobs equation are better than those of CL-20. Considering that this cage compound has a better detonation performance and stability than CL-20, it may he a superior HEDC. [ABSTRACT FROM AUTHOR]

Doping Li atom into higher flexible cyclic polyamines with many amine unit petals (ethyleneimine) forms the n-petal-shaped Li-doped cyclic polyamines (n= 3−5). Three structures, referred to as three-petal-shaped Li-[9]aneN3, four-petal-shaped Li-[12]aneN4, and five-petal-shaped Li-[15]aneN5, with all-real frequencies are obtained at the MP2/6-31+G(d) level. Because the chemical doping with Li and the deformation of the complexant produce more diffuse excess electron, the three molecules with the excess electrons exhibit considerably large static first hyperpolarizabilities (β0) at the MP2 level. Additionally, the β0value increases with increasing the petal number (n) as follows: 52282 (n= 3) < 65505 (n= 4) < 127617 au (n= 5). This shows a new complexant effect on β0, that is, a dependence on the petal number (n) of β0owing to the flexibility of the complexants increasing with the petal number. [ABSTRACT FROM AUTHOR]

A novel method has been proposed to fabricate Nafion/poly(tetrafluoroethylene) (PTFE) composite proton exchange membranes (PEMs) with high durability and high chemical stability. In this method, Nafion ionomers were first converted into the Naform, they were then fixed on PTFE frame micropores, and then the polymer was heat-treated at 270 °C. The chemical stability tests of the novel composite PEMs by Fenton's reagent demonstrate the significant improvement in the chemical durability. The Nafion/PTFE composite PEMs also show an excellent physical stability, and its RH-generated stress is 0.6 MPa at 25 RH% and 90 °C, substantially smaller than 3.1 MPa for pure Nafion membrane under the same conditions. In an in situ accelerating RH cyclic experiment, the degradation in the open circuit voltage (OCV) of the fuel cell assembled with the novel composite PEMs is 3.3 mV/h, significantly lower than 13.2 mV/h for a fuel cell assembled with the commercial Nafion membrane. [ABSTRACT FROM AUTHOR]

By performing density functional theory calculations, we have studied the Markovnikov addition of imidazole to vinyl acetate catalyzed by 1-butyl-3-methylimidazolium hydroxide, bmImOH, a novel basic ionic liquid. The purpose is to show the detailed reaction mechanism, to rationalize the experimental observations, and in particular to better understand the role of bmImOH played in the reaction as a catalyst. Two different reaction pathways (stepwise and concerted) have been charactered and analyzed in detail. It was found that both the cation and anion of bmImOH play important roles in the Markovnikov addition, which decrease the barrier and increase the selectivity of Markovnikov addition. The present results rationalize the early experimental findings well and provide a prototype for theoretically understanding the Markovnikov addition catalyzed by room-temperature ionic liquids. [ABSTRACT FROM AUTHOR]

Unsaturated alcohols and saturated carbonyls are important chemical, pharmaceutical, and biochemical intermediates. We herein report an efficient transfer hydrogenation protocol in which conversion of unsaturated carbonyl compounds to either unsaturated alcohols or saturated carbonyls was catalyzed by Cu(I) N-donor thiolate clusters along with changing hydrogen source (isopropanol or butanol) and base (NaOH or K2CO3). Mechanistic studies supported by DFT transition state modeling indicate that such a chemoselectivity can be explained by the relative concentrations of Cu(I) monohydride and protonated Cu(I) hydride complexes in each catalytic system. [ABSTRACT FROM AUTHOR]

Novel cluster anions Li2F-and Li6F-with alkalide character have been studied in the present paper. In contrast to a typical neutral alkalide, Li2F-contains a F-anion instead of the neutral ligand and forms an alkalide anion F-LiLi-. In addition to a F-anion ligand, Li6F-contains a Li3superalkali cation instead of the alkali metal cation and a Li3-superalkali anion instead of the alkali metal anion, and this alkalide anion can be denoted by F-Li3Li3-, which is supported by NBO charge results. The results indicate that the F-anion can polarize not only the Li atom but also the Li3superalkali to form alkalide anions with excess electrons. For Li2F-, two linear structures (1and 3states) are obtained. For Li6F-, the structure of the 1A1state is a trigonal antiprism capped by the F-anion with C3vsymmetry, while the structure of the 7A‘ state is a slightly distorted trigonal antiprism with Cssymmetry. Due to the excess electrons on the alkali metal and superalkali anions (Li-and Li3-), the alkalide anions Li2F-and Li6F-have large first hyperpolarizabilities (01.116 × 104−1.764 × 105au). For the spin multiplicity effect on electric properties, in these two alkalide anions, the values of the static electric properties, especially the first hyperpolarizabilities, of the high spin states are larger than the corresponding values of the low spin states. For the substitution effect of superalkali atoms, in the two singlet states, as the Li3superalkalis substitute the Li atoms, the value of the mean of polarizability increases, while the values of dipole moment and the first hyperpolarizability decrease. [ABSTRACT FROM AUTHOR]

Chiral quaternary ammonium salts derived from cinchonidine have been applied to catalyze the stereoselective iodolactonizations of trans-5-aryl-4-pentenoic acids leading to a mixture of two regioselectively iodolactonized products with fair to excellent yield (37-98%) and moderate enantioselectivity (exo = 42.0% ee, endo = 31.0% ee) under mild conditions. This work is the first example of asymmetric iodolactonization reaction in the presence of less than a stoichiometric amount of chiral reagent. [ABSTRACT FROM AUTHOR]