Tetrahydrofurane und Lactone,I. Synthese und Reaktionen chiraler 2,5-überbrückter Tetrahydrofurane – ein neuer Weg zu optisch aktiven γ-Lactonen und γ-Bislactonen

Tetrahydrofurans and Lactones, I. - Synthesis and Reactions of Chiral 2,5-Bridged Tetrahydrofurans - A New Approach to Optically Active γ-Lactones and γ-Bislactones Diels-Alder reaction of 3,4-hexamethylenefuran with acrylic acid gives the carboxylic acid 1a with high endo selectivity. 1a was separated into the enantiomers via the α-phenylethylammonium salts. Comparison of the CD spectra of (−)- 1a and (−)- 3 and the X-ray structural analysis of the camphanoyl derivative (−)- 4b lead to the 1R,2S,4S configuration of (−)- 1a as well. The 2,5-bridged tetrahydrofuran (−)- 5 with all-cis and RSS configuration is obtained by ozonolysis of the ester (−)- 1b . (−)- 5 can be oxidized to the γ-lactone (2R,3S)-(−)- 6 with sodium metaperiodate/potassium permanganate in 22% yield. Hydride reduction of (−)- 6 under various conditions leads to the γ-bislactones (−)- 8 and (−)- 9 or to the bislactol (−)- 10 . (−)- 8 has the same absolute configuration as the naturally occuring (−)-canadensolide.     

Optical activity of oriented molecules. comparison of the optical rotatory dispersion and the circular dichroism through the kramers-kronig transform

Circular dichroism and optical rotatory dispersion of anisotropic solutions of testosterone propionate in cholesteryl chloride/cholesteryl laurate have been measured with light propagating parallel to the optical axis of the uniaxial system. Comparison of both effects by the Kramers-Kronig relation excludes falsification by interference with linear birefringence and dichroism effects.     

Hydroxoverbindungen. 9. Barium-Oxohydroxostannat(II) Ba[SnO(OH)]2

Hydroxo Compounds. 9. Barium Oxohydroxostannate(II) Ba[SnO(OH)]₂ The pale yellow barium hydroxostannate(II), to which different stoichiometries have been assigned in the past, is now identified doubtlessly as Ba[SnO(OH)]₂. The compound crystallizes in the monoclinic space group P2₁ (a = 759.4(2) pm, b = 576.2(1) pm, c = 717.4(2) pm, β = 107.67(2)°, Z = 2, R = 0.038, 645 I_hkl) and exhibits a typical layer structure. Ba[SnO(OH)]₂ contains a new structural element in tin(II) chemistry, which is a one dimensional polyanion [SnO(OH)]^? with syndiotactical conformation. In the context with the structures of two Na-hydroxostannates(II) which were characterized recently, the polyanion can be looked at as an intermediate condensation product of a (topotactical ?) reaction to SnO which all known hydroxostannates(II) undergo.     

New synthetic approach to yttrium hydroxoacetates, structural characterization, and use as a precursor for coated conductors

A novel synthetic approach is given for the preparation of a metal-organic lanthanide sol-gel precursor solution and its application for the production of coated conductors. Besides all other problems concerning the technical process itself, the key to a successful deposition of oxide layers is the choice of the precursor solution and the understanding of the mechanism of deposition. Moreover, the isolation and characterization of the species involved in the reaction is very important. Regarding the complex process occurring during the formation of the surface layer, it is obvious that the best choice should have a compound already containing the final composition of the layer. Two compounds of composition [Y(OAc)3(H2O)2]2 and [Y(OAc)3]2(H2O) were isolated from their precursor solution and characterized by X-ray structural analysis. A short outlook will give an insight into the possible bonding mechanisms of the surface layer. These experiments were made with the mixed metal-oxide system yttrium-stabilized zirconium oxide, which is widely used as a substrate for superconducting oxides. A study of the structure of hydrated yttrium acetates, by single-crystal X-ray diffraction, infrared spectra, and elemental analysis demonstrates that there are two separate structures for hydrated yttrium acetates, which play a role as an intermediate in the building of ceramic oxide layers for coated conductors.     

Twista-4,9-diene. Preliminary communication

A synthesis of twista-4,9-diene ( 17 ) from tricyclo[4.3.1.0^3,8]dec-4-en-10-one ( 2 ) is described.     

Zur Chemie und Strukturchemie der Phosphide und Polyphosphide. 27. Bariumdecaphosphid BaP10

Chemistry and Structural Chemistry of Phosphides and Polyphosphides. 27. Bariumdecaphosphide BaP₁₀ Black, reflective crystals of BaP₁₀ are formed by the reaction of BaP₃ with red phosphorus at 1 050 K. The absorption edge at 765 nm corresponds to a band gap of 1.62 eV. The compound is resistant to both acids and bases. The thermal decomposition to Ba₃P₁₄ and then to BaP₃ and other lower phosphides occurs at 725 K. BaP₁₀ crystallizes in the orthorhombic space group Cmc2₁ (No. 36) with 4 formula units (a = 645.2(1), b = 1 258.9(2), c = 1 192.7(2) pm). The structure (632 reflections hkl; R = 0.019) contains the 2-dimensional infinite polyanion [P₁₀^2?], which also characterizes the structure of TlP₅. It originates through the connection of 1-dimensional pentagonal phosphorus tubes, which corresponds to those in the structure of Hittorf's phosphorus and KP₁₅ (bond lengths P? P = 215.0–224.5 pm). Ba is coordinated by 12 P-atoms with distances of 332.7 pm to 374.3 pm.