Highly practical and general synthesis of monodisperse linear pi-conjugated oligoenynes and oligoenediynes with either trans- or cis-olefin configuration

Efficient and practical synthesis of a variety of 1-iodo-4-(trimethylsilyl)but-1-en-3-yne derivatives 1 and 2 with trans- and cis-olefin configuration was described. Their repeated use as building blocks allowed the facile synthesis of trans- and cis-oligoenynes, respectively. Development of a highly practical method for preparing monodisperse trans- and cis-oligoenediynes having the effective conjugation length was also accomplished by using 5 and 4, which can be readily prepared from 1 and 2, respectively.     

A general method for preparing diphosphiranes

Diphosphiranes 3a-3f are obtained by action of diazo derivatives and carbenes on the trans-diphosphene 1. The structures are elucidated by spectroscopic methods. In all cases the cycloaddition reaction is stereoselective.     

合成丙二酸亚异丙酯Mannich碱的新方法

以甲醛和胺作为胺甲基化试剂，合成了丙二酸亚异丙酯及其5－单取代烃基衍 生物的Mannich碱，同时还讨论了这些Mannich碱的化学性质。     

Efficient synthetic method of Psammaplin A

A new concise and efficient synthetic method of Psammaplin A was developed. Psammaplin A was obtained with 50% overall yield in nine steps from p-hydroxybenzaldehyde and ethyl acetoacetate via Knoevenagel condensation and direct nitrosation as key steps. This method might be very efficient to construct a quite diverse library of Psammaplin A type analogs.     

A soft chemistry synthetic method for preparing LiNi0.8Co0.2O2 with enhanced electrochemical performances

Polycrystalline LiNi_0.8Co_0.2O₂ powders were synthesized via the citric acid-assisted liquid phase evaporation method. The precursors are homogenously mixed in the solutions at an atomic scale which is also reflected by the particle distribution of the final products. The optimal synthesis temperature is located at 750?°C where the particle size, crystalline structure, and the cation disorder between Li⁺ and Ni²⁺ ions have been balanced. A high discharge capacity of 191?mAh?g^?? (3.0??.3?V at 30?mA/g) is achieved in the first cycle for the 750?°C-prepared sample with a capacity retention of 89.37% after 96 cycles. Cyclic voltammetry and the differential capacity curves also reveal a moderate stable crystal structure of 750?°C-prepared LiNi_0.8Co_0.2O₂ during the prolonged cycles.     

5,10,15,20-中位-四(4-氨基苯基)卟吩合成方法的改进

在还原剂维生素C存在下,将4-氨基苯甲醛与吡咯在丙酸中缩合得到5,10,15,20-中位-四(4-氨基苯基)卟吩,操作简单,产率高于文献方法。     

New synthetic route for preparing rattle-type silica particles with metal cores

Rattle-type silica particles with metal cores, applicable to catalysts and metal/inorganic composite coating materials, were prepared by the pre-shell/post-core method that can control the size of metal cores inside silica capsules and exchange from metal cores into different ones with a metal displacement reaction.     

Efficient methods for configuration interaction calculations

Advanced techniques are developed to provide efficient economic treatment of the large scale eigenvalue problem posed when configuration interaction is carried out on SCF basis sets of moderate size. When the characteristic properties of the hamiltonian matrix are examined in light of the type of solution required, partitioning of the configuration space is shown to result in an expansion of the problem about a limited core of states, where the small but cumulative interactions of vast regions of the remaining space are reduced to the form of an effective potential. With proper selection of the core, the evaluation of this potential can be readily and accurately truncated to a level involving minimum expenditure in time and effort. In particular only diagonal elements and a strip of the full CI matrix are required to achieve an accuracy of 1 – 5 kcal/mole with complete treatment for configuration spaces of order tens of thousands. In addition, a close look at current theory on the generation of matrix elements between spin symmetry adapted configurations leads to simplified expressions where the matrix elements are derived in the form of a weighted sum of molecular integrals in which the weighting coefficients represent the integrated value of the wavefunctions over spin coordinates. For typical cases of low multiplicity and limited numbers of open shells the list of unique parameters needed to generate all weights are shown to be readily stored as a program library. Actual times for matrix element generation are believed to be an order of magnitude faster than current techniques. Practical demonstration of the accuracy and efficiency of the method is provided by calculations on formaldehyde, water, and ethylene.     

The direct configuration interaction method for general multireference expansions: Symmetric group approach

A computer implementation of the direct configuration interaction method formulated within the symmetric group approach is discussed. The formulation allows for an open-shell as well as for a multiconfigurational reference state. The number of all necessary formulas, derived by a computer for each integral type rather than for the individual integrals, is lower than in the currently existing techniques, including the unitary group approach. The logical structure of a general program for singly and doubly excited configurations is outlined. The efficiency of the symmetric group approach is demonstrated on a recently developed program, restricted to one reference state only.     

A new method for preparing carbenes

Russian Chemical Bulletin -     

The direct configuration interaction method with a contracted configuration expansion

A variant of the configuration interaction method is outlined. There are four characteristic features of the method. First, the freezing, contraction of coefficients in the configuration expansion. In the present approach Rayleigh-Schrödinger perturbation theory has been used for this purpose. Second, the use of the direct CI-method to construct hamiltonian matrix elements between functions with contracted coefficients, in only one sequential read of the molecular integrals. Third, a diagonalization of the resulting small matrix. Fourth, an important computational advantage in that only one CI-vector is needed in core storage instead of two as in the usual direct CI-method. The method has been programmed for the case of all single and double replacements from a spin-unrestricted Hartree-Fock determinant. Test calculations indicate that usually less than 2% of the correlation energy is lost because of the contraction of the CI-expansion. A possibility to avoid the major part of the integral transformation and work directly with atomic basis functions is also discussed.     

Redox-active ionic-liquid-assisted one-step general method for preparing gold nanoparticle thin films: applications in refractive index sensing and catalysis

We describe a general one-step facile method for depositing gold nanoparticle (GNP) thin films onto any type of substrates by the in situ reduction of AuCl(3) using a newly designed redox-active ionic liquid (IL), tetrabutylphosphonium citrate ([TBP][Ci]). Various substrates such as positively charged glass, negatively charged glass/quartz, neutral hydrophobic glass, polypropylene, polystyrene, plain paper, and cellophane paper are successfully coated with a thin film of GNPs. This IL ([TBP][Ci]) is prepared by the simple neutralization of tetrabutylphosphonium hydroxide with citric acid. We also demonstrate that the [TBP][Ci] ionic liquid can be successfully used to generate GNPs in an aqueous colloidal suspension in situ. The deposited GNP thin films on various surfaces are made up of mostly discrete spherical GNPs that are well distributed throughout the film, as confirmed by field-emission scanning electron microscopy. However, it seems that some GNPs are arranged to form arrays depending on the nature of surface. We also characterize these GNP thin films via UV-vis spectroscopy and X-ray diffractometry. The as-formed GNP thin films show excellent stability toward solvent washing. We demonstrate that the thin film of GNPs on a glass/quartz surface can be successfully used as a refractive index (RI) sensor for different polar and nonpolar organic solvents. The as-formed GNP thin films on different surfaces show excellent catalytic activity in the borohydride reduction of p-nitrophenol.     

Efficient configuration selection scheme for vibrational second-order perturbation theory

A fast algorithm of vibrational second-order Moller-Plesset perturbation theory is proposed, enabling a substantial reduction in the number of vibrational self-consistent-field (VSCF) configurations that need to be summed in the calculations. Important configurations are identified a priori by assuming that a reference VSCF wave function is approximated well by harmonic oscillator wave functions and that fifth- and higher-order anharmonicities are negligible. The proposed scheme has reduced the number of VSCF configurations by more than 100 times for formaldehyde, ethylene, and furazan with an error in computed frequencies being not more than a few cm(-1).     

Efficient synthesis of cis- and trans-3,4-dihydroxy-3,4-dihydromollugin

An efficient synthesis of naturally occurring compounds isolated from Pentas longiflora, cis-3,4-dihydroxy-3,4-dihydromollugin 2, and trans-3,4-dihydroxy-3,4-dihydromollugin 3 is described. The O-protected mollugins were dihydroxylated using OsO4 to achieve the corresponding cis-dihydroxy derivatives in excellent yield. The synthesis of trans-3,4-dihydroxy-3,4-dihydromollugin was achieved using Oxone in good yield. A mechanism for the formation of cis-3,4-dihydroxymollugin acetonide from the reaction of mollugin with Oxone is proposed.     

New method for preparing saturated and unsaturated aliphatic polyurethanes

Saturated and unsaturated aliphatic polyurethane were obtained from three different routes. In route 1, 1,4-dichloro-2-butene, sodium cyanate, and methanol were reacted to give dimethyl 2-butene-1,4-dicarbamate. This is hydrogenated easily to give dimethyl butane-1,4-dicarbamate. Ester exchange reaction of this compound with glycol gave saturated aliphatic polyurethane. In another procedure, route 2, 1,4-dichloro-2-butene, sodium cyanate and excess glycol were reacted to give bis(ω-hydroxyalkyl)-2-butene-1,4-dicarbamate. This was hydrogenated to give bis(ω-hydroxyalkyl)-butane-1,4-dicarbamate. A glycol elimination reaction gave poly(polymethylene tetramethyl-enedicarbamate). By route 3, 1,4-dichloro-2-butene, sodium cyanate, and glycol were reacted to give poly(polymethylene 2-butene-1,4-dicarbamate), a new unsaturated aliphatic polyurethane.     

A direct method for preparing ethyldichlorosilane and its comparison with known alternative methods

Various methods, alternative to direct synthesis, for preparing an important commercial organosilicon monomer, ethyldichlorosilane, were studied in detail. The methods, including organomagnesium and organoaluminum procedures, hydrosilylation, and combined methods, were analyzed from the viewpoint of feasibility of laboratory and small-tonnage commercial production, and their advantages and drawbacks were revealed.     

Efficient synthetic method of multisubstituted allenes from the reactions of allylindium reagents with 3 degree-propargyl alcohols

An efficient synthetic method of tri- and tetra-substituted allenes having an allyl and methallyl group was developed by the reactions of allylindium reagents generated in situ from indium and allyl bromides with 3 degree-propargyl alcohols.     

Efficient syntheses and ring-opening reactions of trans- and cis-oxazoline-5-carboxylates

[formula: see text] cis- and trans-Oxazoline-5-carboxylates were synthesized efficiently from isopropyl trans-cinnamate utilizing the Sharpless AA reaction. trans-Oxazoline was much more reactive than the cis-isomer toward ring opening reactions. From ab initio molecular calculations, the cis-isomer was predicted to be less reactive than the trans-isomer by 2.7 kcal/mol. Both syn and anti acetylthio esters and anti diamino esters were synthesized from these cis- and trans-oxazoline-5-carboxylates.