Enantioselective Synthesis of Possible Diastereomers of Heptadeca-1-ene-4,6-diyne-3,8,9,10-tetrol; Putative Structure of a Conjugated Diyne Natural Product Isolated from Hydrocotyle leucocephala

Enantioselective synthesis of possible diastereomers of heptadeca-1-ene-4,6-diyne-3,8,9,10-tetrol, a structure proposed for the natural product isolated from Hydrocotyle leucocephala is accomplished. The reported spectral data of the natural product did not match those of any of the isomers that were synthesized and established that the structure proposed for the natural product is not correct and requires revision.

Growth and characterization of $SrBi_{2}Nb_{2}O_{9}$ thin films by pulsed-laser ablation

Polycrystalline films of SrBi2Nb2O9 were grown using pulsed-laser ablation. The ferroelectric properties were achieved by low-temperature deposition followed by a subsequent annealing process. The lower switching voltage was obtained by lowering the thickness, which did not affect the insulating nature of the films. The hysteresis results showed an excellent square-shaped loop with results (P-r=6 mu C/cm(2), E-c=100 kV/cm) in good agreement with earlier reports. The films also exhibited a dielectric constant of 250 and a dissipation factor of 0.02. The transport studies indicated an ohmic behavior, while higher voltages induced a bulk space charge.

3,3,6,6-Tetramethyl-9-phenyl-3,4,5,6-tetrahydro-9H-xanthene-1,8(2H,7H)-dione

In the title compound, C23H26O3, the three six-membered rings of the xanthene system are non-planar, having total puckering amplitudes, QT, of 0.443 (2), 0.202 (2) and 0.449 (2) Å. The central ring adopts a boat conformation and the outer rings adopt sofa conformations. The crystal structure is stabilized by van der Waals interactions.

A thermal molecular migration in the solid-state - structures of isomeric 5-amino-4-(2,6-dichlorophenyl)-1-(2-nitrophenyl)-1h-1,2,3-triazole (yellow form i) and 4-(2,6-dichlorophenyl)-5-(2-nitroanilino)-2h-1,2,3-triazole (red form-ii), c14h9cl2n5o2

Yellow form (I): Mr= 350.09, monoclinic, P2Jn, Z--4, a=9.525(1), b=14.762(1), c= 11.268(1),/t, fl= 107.82 (1) o , V= 1508.3 A 3 , Din(flotation in aqueous KI)= 1.539 (2), D x= 1.541 (2) g cm -3, #(Cu Ka, 2 = 1.5418 A) = 40.58 cm -~, F(000) = 712, T= 293 K, R = 8.8% for 2054 significant refections. Red form (II): Mr= 350.09, triclinic, Pi, Z=2, a=9.796(2), b= 10.750 (2), c= 7.421 (1)A, a= 95.29 (2), fl= 0108-2701/84/111901-05501.50 70.18 (1), y = 92-.76 (2) °, V= 731.9 A 3, Din(flotation in KI) = 1.585 (3), D x = 1.588 (3) g cm -3, ~t(Cu Ka, 2 = 1.5418/~) = 40.58 cm -1, F(000) = 356, T=293 K, R = 5.8% for 1866 significant reflections. There are no unusual bond distances or angles. The triazole and two phenyl rings are planar. On the basis of packing considerations the possibility of intermolecular interactions playing a role in the reactivity of the starting material is ruled out.

Complexes of lanthanide perchlorates with the open-chain pentadentate ligand n,n,$n^{'},n^{'}$-tetramethyl-3,6,9-trioxaundecane diamide

Complexes of lanthanide perchlorates with the ligand N,N,N,N-tetra-methyl-3,6,9-trioxaundecane diamide (TUD) of the composition Ln(TUD)2-(ClO4)3 (Ln triple bond; length as m-dash La, Nd, Ho, Er, Y) were isolated. Electrical conductivity values indicate that all the perchlorate groups are ionic. IR and nuclear magnetic resonance (1H and 13C) data prove that the ligand coordinates to the metal via the three ether oxygens and the two carbonyl oxygens. A probable coordination number of ten can be assigned for all the complexes.

2-(p-Chlorophenyl)-3-nitro-2H-chromene

C15H10C1NO3, Mr=287.70, triclinic, PI, Z= 2, F(000)= 296, a = 5.422 (1), b = 9.624 (1), c= 12.636 (2) A, ~= 76.66 (2), fl= 78.67 (2), ~= 87.97 (2) ° , V=629.03 A 3, Din= 1.507 (3), Ox= 1.519Mgm -3, 2(CuKa)=l.5418A, p=26.25mm -~, T= 413 K, final R = 0.0577 for 1859 observed reflections [I>2.5e(/)]. Bond lengths [1.512(5)A] and angles [109.2 (3) °] at the phenyl substitution site are comparable with those in other molecules. The bond angle at the nitro substitution site C(7)-C(8)-C(9) is 122.9 (3) ° owing to the electron-withdrawing character of the nitro group. The pyran ring adapts a half-chair conformation.

Aspects of tautomerism 9-solvolysis of normal and pseudo phthaloyl chlorides

Solvolysis of normal and pseudo phthaloyl chlorides in aqueous acetone and in aqueous dioxane has revealed that the former solvolyses about hundred-fold faster than the latter. Contrary to the accepted belief, there is no evidence for equilibrium between the normal and the pseudo forms of phthaloyl chloride, under a variety of conditions.

Crystallization and preliminary X-ray studies of the anti-T lectin from peanut (Arachis hypogaea)

The anti-T lectin from peanut (Arachis hypogaea) crystallizes in the orthorhombic space group P21212 with one tetrameric molecule (Mr 110,000) in the asymmetric unit in a cell of dimensions a = 129.3 Å, B = 126.9 Å and C = 76.9 Å. The crystals are suitable for high resolution work.

Gas-crystal photoreaction: the structures of 4,4'-dimethoxy(thiobenzophenone) (I), C15H14O2S, and 4,4'-bis(dimethylamino)thiobenzophenone (II), C17H20N2S

(I): M r = 258.34, triclinic, Pi, a = 9.810 (3), b=9.635(3), e=15.015(4)A, a=79.11(2), #= 102.38 (3), y = 107.76 (3) o, V= 1308.5 A 3, Z = 4, Din= 1.318 (3) (by flotation in KI solution), D x = 1.311 g cm -3, Cu Ka, 2 = 1.5418/~, g = 20-05 cm -1, F(000) = 544, T---- 293 K, R = 0.074 for 2663 reflections. (II): M r = 284.43, monoclinic, P2~/c, a= 17.029 (5), b=6.706 (5), c= 14.629 (4), t= 113.55 (2) ° , V=1531.4A 3, Z=4, Dm=1.230(5) (by flotation in KI solution), Dx= 1.234gem -3, Mo Ka, 2 = 0.7107 A, g = 1.63 cm-1; F(000) = 608, T= 293 K, R = 0.062 for 855 reflections. The orientation of the C=S chromophores in the crystal lattice and their reactivity in the crystalline state are discussed. The C--S bonds are much shorter than the normal bond length [1.605 (4) (I), 1.665 (8) A (II) cf. 1.71 A].

Ni(II)chelates of 4,9-dimethyl-5,8-dizadodeca-4,8-diene-2,11-dione-3,10-diphenyl hydrazone and related molecules

Syntheses and structural characterization of Ni(II) chelates of a new series of symmetric and unsymmetric tetradentate linear ligands are described. Preparative routes involve either the direct reaction between a metal complex and arene diazonium diazonium salts or a simple metal incorporation into the independently synthesized ligands. Recent X-ray structure determination of 4,9-dimethyl-5,8-diazadodeca-4,8-diene-2,11-dione-3,10-di(4′-methyl phenyl) hydrazonatonickel(II) complex reveals the geometry around the Ni(II) to be very close to square planar. The expected distortion because of the disposition of bulky aromatic groups on the neighbouring nitrogens is minimized by their projection in the opposite directions from the plane. PMP, IR and electronic spectral data for the complexes are quite in agreement with this structure.

Crystal and molecular structure of 15-bromolongibornane-8,9-dione

The crystal and molecular structure of the title compound (1) has been determined by the heavy-atom method from 1038 observed three-dimensional photographic data. Crystals are orthorhombic, with a = 20.07 ± 0.02, b= 10.05 ± 0.02, c= 7.31 ± 0.01 Å, space group P212121, with Z= 4. The structure was refined by block diagonal leastsquares to R 0.099. The conformation of the norbornane moiety is discussed. The seven-membered ring portion of the molecule adopts an approximate chair conformation. The packing of the molecules in the crystal is mainly a consequence of van der Waals interactions.

Bromination of Intermolecular Chelate Linkage Isomers of 3-Oximino-4,9-Dimethyl (or 4,7,9-Trimethyl)-5,8-Diazadodeca-4,8-Diene-2,11-Dionato Nickel(II)

The reaction of the title complexes (FIG. 1) with N-bromosuccinimide or bromine in chloroform yields isomeric bromo complexes on substitution of the γ-CH carbon proton by bromine. The brominated products have been characterised by ir, pmr, electronic absorption spectra, conductivity and magnetic susceptibility measurements. The linkage isomerisation of the brominated products in chloroform has been shown to depend on the diamine residue.

D.c. and a.c. polarographic behaviour of vanadium-glycine complexes

A detailed investigation of the d.c. polarographic behaviour of vanadium(V),-(IV) and -(III) in glycine solutions has been made keeping the total glycine concentration at 0.1, 0.5 and 1.0 M and varying the pH of the solution. Experiments keeping the pH constant (using different ratios of glycine and glycine anion) and varying the glycine anion concentration, and also in predominantly anion solutions, have been made.

Structure of bis(thiocyanato-N)bis(thiosemicarbazide-N1,S)nickel(II): a redetermination

[Ni(NCS)2(CHsN3S)2], Mr = 356.7, monoclinic, P21/c , a = 5-297 (1), b = 7.869 (1), c - 16-078 (2) A,/3 = 91.53 (1) °, V-= 669.9 A 3, Z= 2, Om = 1"76, Dx = 1"771 g cm -3, A(Mo Ka) = 0-71069 ]k, /.~ = 19"9 cm-l, F(000) = 364, T = 295 K, final R = 0.026 for 1576 significant [F > 10g(F)] reflections. The complex lies on a crystallographic centre of symmetry. The Ni atom is octahedrally coordinated by two thiocyanates (through N atoms) and by two thiosemicarbazide molecules (through hydrazinic N and S atoms). The crystal structure is stabilized by N--H...S hydrogen bonds. Early work on this structure [Garaj & Dunaj-Jurco (1968). Chem. Commun. p. 518] used photographic data and was refined to R = 0-13 for 512 reflections.