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Dichlorido(3-phenylindenylidene)bis(triphenylphosphane)ruthenium(II) tetrahydrofuran disolvate
(2011)
The RuII atom in the title compound, [RuCl2(C15H10)(C18H15P)2]·2C4H8O, has a distorted square-pyramidal conformation. The P and Cl atoms are at the base of the pyramid and the Ru-Cindenylidene bond is in the axial position. The two Cl ligands and the two phosphane ligands are in trans positions. The Cl-Ru-Cl and P-Ru-P angles are 157.71 (2) and 166.83 (2)°, respectively. The two independent tetrahydrofuran (THF) solvent molecules are disordered. One THF molecule was refined using a split-atom model. The second THF molecule was accounted for by using program PLATON/SQUEEZE [Spek (2009). Acta Cryst. D65, 148-155]. The molecular conformation shows three intramolecular C-H...Cl contacts and two C-H...[pi] interactions while the crystal packing features an intermolecular C-H...Cl contact and two very weak intermolecular C-H...[pi] contacts.
A new procedure for the synthesis of 2-(4-propylphenyl)ethanol is provided. This new procedure significantly reduces side-products as 1-(4-propylphenyl)ethanol and 2-bromoethanol, which are obtained when using the previously known procedure. Only with the new procedure an efficient purification on the large scale needed for avoided-level-crossing muon-spin resonance experiments was possible.
Structural details of the title compound could be derived from an X-ray structure analysis of a crystalline derivative, the nitrobenzoyl ester.
Pyrazolyl-substituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives have been synthesized by reaction of 1,4-benzoquinone and 1,4-naphthoquinone, respectively, with pyrazole. Cyclovoltammetric measurements have shown that 1,4-benzoquinone possesses the potential to oxidize 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene. The 2,5-bis(pyrazol-1-yl)- 1,4-dihydroxybenzene reacts with air to give quantitatively black insoluble 2,5-bis(pyrazol-1-yl)-1,4- quinhydrone. Black crystals of 2,5-bis(pyrazol-1-yl)-1,4-quinhydrone suitable for X-ray diffraction were grown from methanol at ambient temperature (monoclinic C2/c). The poor yields of pyrazolylsubstituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives can be explained by the formation of insoluble black quinhydrons in the reaction of benzoquinone and naphthoquinone with pyrazole. The dianions of 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene react with oxygen to give the corresponding semiquinone anions. 2,5-Bis(pyrazol-1-yl)-1,4-benzoquinone shows two reversible one-electron reduction processes in cyclovoltammetric measurements, whereas pyrazolyl-substituted 1,4-dihdroxybenzene and -naphthene derivatives undergo irreversibile electrontransfer processes.
The crystal structure of C12H11N2SiCl3 (monoclinic, P21/m, Z = 2, with a: 9.284(4), b: 7.226(2), c: 10.832(5) Å, β = 115.14(3)°) was refined to R(F) =0.035 from 1228 independent reflections. A trigonal bipyramidal, pentacoordinate silicon is observed. The chelated complex shows two different Si−N bonds, a coordinative bond (1.984(2) Å) between Si and N on the axial position and a Si−N single bond (1.737(3) A, equatorial plane), introduced by chemical reaction. The coordinative bond is 14.2% longer than the Si−N single bond. The lengthening of the coordinative bond in the present case is compared with distances in other extracoordinated silicon compounds.
A chiral analog of the bicyclic guanidine TBD : synthesis, structure and Brønsted base catalysis
(2016)
Starting from (S)-β-phenylalanine, easily accessible by lipase-catalyzed kinetic resolution, a chiral triamine was assembled by a reductive amination and finally cyclized to form the title compound 10. In the crystals of the guanidinium benzoate salt the six membered rings of 10 adopt conformations close to an envelope with the phenyl substituents in pseudo-axial positions. The unprotonated guanidine 10 catalyzes Diels–Alder reactions of anthrones and maleimides (25–30% ee). It also promotes as a strong Brønsted base the retro-aldol reaction of some cycloadducts with kinetic resolution of the enantiomers. In three cases, the retro-aldol products (48–83% ee) could be recrystallized to high enantiopurity (≥95% ee). The absolute configuration of several compounds is supported by anomalous X-ray diffraction and by chemical correlation.
Single crystals of the title compound, C10H11NO4, an intermediate in the industrial synthesis of yellow azo pigments, were obtained from the industrial production. The molecules crystallize as centrosymmetic dimers connected by two symmetry-related N—H⋯O=C hydrogen bonds. Each molecule also contains an intramolecular N—H⋯O=C hydrogen bond. The dimers form stacks along the a-axis direction. Neighbouring stacks are arranged into a herringbone structure.
The title compound, C12H20N4O, undergoes a phase transition on cooling. The room-temperature structure is tetragonal (P43212, Z′ = 1), with the methoxybornyl group being extremely disordered. Below 213 K the structure is orthorhombic (P212121, Z′ = 2), with ordered molecules. The two independent molecules (A and B) have very similar conformations; significant differences only occur for the torsion angles about the Cbornyl—Ctetrazole bonds. The independent molecules are approximately related by the pseudo-symmetry relation: xB = −1/4 + yA, yB = 3/4 - xA and zB = 1/4 + zA. In the crystal, molecules are connected by N—H⋯N hydrogen bonds between the tetrazole groups, forming a pseudo-43 helix parallel to the c-axis direction. The crystal studied was a merohedral twin with a refined twin fraction value of 0.231 (2).
The title molecule, C34H28I4·4C6H6, has crystallographic 4 symmetry and crystallizes with four symmetry-related benzene solvent molecules. The phenyl group is eclipsed with one of the adamantane C—C bonds. The tetraphenyladamantane units and the benzene solvent molecules are connected by weak intermolecular phenyl–benzene C—H⋯π and benzene–benzene C—H⋯π interactions. In the crystal, molecules are linked along the c-axis direction via the iodophenyl groups by a combination of weak intermolecular I⋯I [3.944 (1) Å] and I⋯π(phenyl) [3.608 (6) and 3.692 (5) Å] interactions.
The title compound, C37H67NO13·2C2H6OS·1.43H2O, is a macrolide antibiotic with better solubility and better dermal penetration abilities than erythromycin A itself. The asymmetric unit of this form contains one erythromycin A molecule, two dimethyl sulfoxide (DMSO) solvent molecules, a fully occupied water molecule and a partially occupied water molecule with an occupancy factor of 0.432 (11). The 14-membered ring of the erythronolide fragment has a conformation which differs considerably from that in erythromycin A dihydrate [Stephenson, Stowell, Toma, Pfeiffer & Byrn (1997[Stephenson, G. A., Stowell, J. G., Toma, P. H., Pfeiffer, R. R. & Byrn, S. R. (1997). J. Pharm. Sci. 86, 1239-1244.]). J. Pharm. Sci. 86, 1239–1244]. One of the two DMSO molecules is disordered over two orientations; the orientation depends on the presence or absence of the second, partially occupied, water molecule. In the crystal, erythromycin molecules are connected by O—H⋯O hydrogen bonds involving the hydroxy groups and the fully occupied water molecule to form layers parallel to (010). These layers are connected along the b-axis direction only by a possible hydrogen-bonding contact involving the partially occupied water molecule.