A Convenient Regiospecific Synthesis of New Conjugated Tetrazole Derivatives via the Reaction of Dienones with the Tetrachlorosilane-Sodium Azide Reagent and their NMR Structural Assignment

Summary. Several new 1-aryl-, aralkyl-, and heteroaryl-5-(4-phenylbuta-1,3-dienyl)tetrazole derivatives and annulated tetrazole derivatives were efficiently and regiospecifically prepared in nearly quantitative yield via a facile one step reaction of dienones with a combination of tetrachlorosilane and sodium azide in acetonitrile under mild conditions. A complete structure assignment of three representative examples of the tetrazoles was achieved by advanced 2D NMR measurements including COSY, TOCSY, HSQC, HMBC, NOESY, and ROESY experiments.Received March 17, 2003; accepted March 18, 2003 Published online July 28, 2003     

Convergence behavior of the density-matrix renormalization group algorithm for optimized orbital orderings

The density-matrix renormalization group algorithm has emerged as a promising new method in ab initio quantum chemistry. However, many problems still need to be solved before this method can be applied routinely. At the start of such a calculation, the orbitals originating from a preceding quantum chemical calculation must be placed in a specific order on a one-dimensional lattice. This ordering affects the convergence of the density-matrix renormalization group iterations significantly. In this paper, we present two approaches to obtain optimized orderings of the orbitals. First, we use a genetic algorithm to optimize the ordering with respect to a low total electronic energy obtained at a predefined stage of the density-matrix renormalization group algorithm with a given number of total states kept. In addition to that, we derive orderings from the one- and two-electron integrals of our test system. This test molecule is the chromium dimer, which is known to possess a complicated electronic structure. For this molecule, we have carried out calculations for the various orbital orderings obtained. The convergence behavior of the density-matrix renormalization group iterations is discussed in detail.     

Tetrakis(trifluormethyl)tellur (CF3)4Te [1]

(CF₃)₄Te is formed from the reaction of (CF₃)₂TeCl₂ with (CF₃)₂Cd·glyme in CH₃CN at ?10°C via the intermediate (CF₃)₃TeCl as a yellow liquid and identified by n.m.r. and mass spectra.     

Syntheses and Properties of Two Heterocyclically Substituted Hypericin Derivatives: 10,11-Dibenzothiazolyl-10,11-didemethylhypericin and 10,11-Dibenzoxazolyl-10,11-didemethylhypericin

Summary. The syntheses of the two heterocyclically substituted title hypericin derivatives were achieved starting either from 6-benzothiazolyl-tri-O-methyl-6-demethylemodin or 6-benzoxazolyl-tri-O-methyl-6-demethylemodin. The use of microwave assisted synthesis for the preparation of these anthraquinone synthons and the chemical as well as photochemical properties of the corresponding unique hypericin derivatives, which might constitute new photodynamic therapy agents, are reported. The tautomeric and stereochemical aspects of these hypericin derivatives were investigated by means of semiempirical calculations (AM1).     

Square-planar coordinated polyanions of palladium, platinum, and gold stannaborate [SnB11H11]2- coordination chemistry

The tetrasubstituted polyanions of platinum, palladium, and gold [M(SnB(11)H(11))(4)](x-) (x=6, M=Pd, Pt; x=5, M=Au) have been prepared and characterized by single-crystal X-ray diffraction, elemental analysis, IR, Raman, (11)B, and (119)Sn heteronuclear NMR spectroscopy. In the case of the platinum derivative [Bu(3)MeN](6)[Pt(SnB(11)H(11))(4)] (2) (119)Sn M?ssbauer spectroscopy has been carried out. The isolated salts are stable towards moisture and air and the complexes 2 and 3 were treated with 1,3-bis(diphenylphosphino)propane (dppp) to give the respective substitution products [Bu(3)MeN](2)[(dppp)M(SnB(11)H(11))(2)] (M=Pd, Pt).     

A Convenient Regiospecific Synthesis of New Conjugated Tetrazole Derivatives via the Reaction of Dienones with the Tetrachlorosilane-Sodium Azide Reagent and their NMR Structural Assignment

Several new 1-aryl-, aralkyl-, and heteroaryl-5-(4-phenylbuta-1,3-dienyl)tetrazole derivatives and annulated tetrazole derivatives were efficiently and regiospecifically prepared in nearly quantitative yield via a facile one step reaction of dienones with a combination of tetrachlorosilane and sodium azide in acetonitrile under mild conditions. A complete structure assignment of three representative examples of the tetrazoles was achieved by advanced 2D NMR measurements including COSY, TOCSY, HSQC, HMBC, NOESY, and ROESY experiments.     

Neue Fluropalladate(II)

New Fluoropalladates(II) Single crystal investigations on \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} {[6][4]} \\ {{\rm CsPdPdF}_{\rm 5} } \\ \end{array} $\end{document} (orange brown) demonstrate the close structural relationship to the CsAgFeF₆ – and CsNiNiF₆-type, respectively. One half of the Pd²⁺ ions is surrounded octahedrally, whereas the other half, because of the “absence” of one F^?, is coordinated planar quadratically. CsPd₂F₅ crystallizes orthorhombic (Imma – D, No. 74; Z = 4) with a = 6.53₃, b = 7.86₂, c = 10.79 Å (four circle diffractometer data). From Guinier data are isotypic CsMgPdF₅ (yellow, a = 6.603(2), b = 7.415(2), c = 10.548(3) Å), CsZnPdF₅ (beige, a = 6.576(1), b = 7,483(2), c = 10.645(2) Å), CsNiPdF₅ (yellow, a = 6.499(1), b = 7.504(2), c = 10.575(3) Å) and CsCoPdF₅ (brown, a = 6.527(1), b = 7.553(1), c = 10.659(2) Å). Besides of CsPd₂F₅ there exist compounds of the composition Me₃PdF₅ on the alkali-rich side of the system MeF/PdF₂. Single crystal investigations for Rb₃PdF₃ (yellow, P4/mbm–D, No. 127; Z = 2) led to a = 7.46₇, c = 6.49₇ Å (four circle diffractometer data). Isotypic are (single crystal data) Cs₃PdF₅ (yellow, a = 7.84₈, c = 6.68₈ Å) and Rb₂CsPdF₅ (yellow, ordered distribution of the alkali ions, a = 7.57₅, c = 6.44₅ Å).     

Reaction of 1,4-pentadiyne with diethylaminotrimethylstannane

The reaction between 1,4-pentadiyne and diethylaminotrimethylstannane leads predominantly to (E)-2-diethylamino-4-trimethylstannyl-2,4-pentaenyne (with either a 1/1 or 1/2 mol ratio of 1,4-pentadiyne and diethylaminotrimethylstannane). With 1/2 stoicheiometry 1,1,5-tris(trimethylstannyl)penta-1,2-dien-4-yne is formed as a minor product. ¹³C and ¹¹⁹Sn NMR data are reported.     

The addition of diazomethane to β-ethynylpyridines

The action of diazomethane on -ethynylpyridines substituted in the pyridine ring or analogous compounds with an alkyl group in place of the acetylenic hydrogen atom has given 3-(pyridin-3-yl)pyrazoles. When the acetylenic hydrogen atom is replaced by an electron-accepting carboxyl group, the polarization of the triple bond interferes with the reaction, which then leads to a mixture of 3- and 4-(pyridin-3-yl)pyrazoles with the simultaneous methylation of the nitrogen of the pyrazole ring.