F. van Bolhuis

The X-ray structure and MNDO calculations of α-terthienyl: A model for polythiophenes

Abstract The X-ray structure of α-terthienyl reveals two identical, crystallographically-independent molecules in the unit cell. Neighbouring thiophene moieties in α-terthienyl are placed antiparallel, while the molecule is almost planar, with torsional angles between the rings of about 6 – 9°. MNDO calculations of α-terthienyl show that great care should be taken in using calculations of this type for geometrical optimizations of polythiophenes.

Synthesis and crystal structures of two dialkyl-substituted sexithiophenes

Abstract Two stereoregular dialkyl-substituted sexithiophenes have been synthesized and their X-ray structures revealed. Both molecules have neighbouring thiophene rings placed antiparallel and the molecules are almost planar. The torsional angles between the rings vary from 5 to 11°. The alkyl side chains are in the planar zigzag form and almost confined to the plane of the thiophene backbone.

Asymmetric 1,4-Additions to 5-Alkoxy-2(5H)-furanones Enantioselective Synthesis and Absolute Configuration Determination of β-Amino-γ-butyrolactones and Amino Diols

Abstract The synthesis of enantiomerically pure β-amino-δ-butyrolactones via asymmetric conjugate addition of various amines to 5-menthyloxy-2(5H)-furanone is described. This route provides access to new multifunctionalhomochiral building blocks. The absolute configuration of the β-amino-δ-butyrolactones is established by X-ray analysis and 1H NMR correlation. Theconjugate addition of amines to 2[5H]-furanone, 5-alkyl-2[5H]-furanones and 5-alkoxy-2[5H]-furanones was studied and an enhanced reactivity was observed in 2[5H]-furanones due to a γ-alkoxy-effect. The synthetic utility of the asymmetric amine addition is illustrated in an efficient route to various optically pure 2-amino-1, 4-butanediols.

Transition metal catalyzed asymmetric cross coupling reactions. New ligands and the effects of added salts. Crystal structures of [Ph2PCH2CH{(CH2)3SMe}NMe2]·PdCl2 and [Ph2PCH2CH{(CH2)2SMe}NMe2]·PdCl2

Tridendate ligands have been derived from the amino acids lysine, methionine, methionine sulfoxide, and homomethionine by dimethylation at nitrogen and reduction of the carboxyl group followed by substitution of hydroxyl by the diphenylphosphino group. These ligands are effective in promoting the Ni0 or Pd0 catalyzed cross coupling of the Grignard reagent of 1-chloro-1-phenylethane with vinyl bromide. The enantiomeric excesses found for coupling product formed in the presence of these ligands exceed those expected on the grounds solely of a steric effect of the amino acid side chain. A special effect of the heteroatom in the side chain is indicated. X-ray diffraction studies of the PdCl2 complexes of the ligands derived from methionine and homomethionine confirm the expected coordination of the transition metal atom by the phosphino and amino centers and reveal that there is no significant ligation of sulfide in these dipositive cations. Not only heteroatoms in the side chain but also the presence of other metal cations in solution profoundly affect the course of reaction. When ZnBr2 is added to the Grignard reagent derived from 1-chloro-1-phenylethane, the rate of Ni0 or Pd0 catalyzed coupling with vinyl bromide increases and the direction of the enantioselection is reversed. Similar effects are observed with ZnI2, but ZnCl2 has a pronounced inhibitory effect on the cross coupling. Other added salts have little effect. This switch in enantioselectivity induced by zinc halides allows a formal synthesis of the analgesic ibuprofen starting from use of a single chiral ligand in the Ni0 catalyzed cross coupling of (4-isobutyl)-1-phenyl-1-chloroethane with vinyl bromide. Subsequent oxidation of the double bond leads to ibuprofen, the enantiomer obtained depending on the reaction conditions.

Bimetallic Oxidation Catalysts. Oxygen Insertion into an Aryl–Hydrogen Bond of a Binuclear Copper(I) Complex

The binuclear copper(I) complex of 1,3-bis[N-(2-pyridylethyl)formimidoyl]benzene reacts with molecular oxygen to give a phenoxy- and hydroxy-bridged binuclear copper(II) complex; the structures of both complexes have been determined by X-ray crystallography.

The Crystal Structure of a Phenyliminomethyldicyclopentadienyltitanium(III) Complex, Cp2Ti-η2-C6H5CN-2,6-(CH3)2C6H3

Abstract The crystal structure of Cp2TiC6H5CN-2,6-(CH3)2C6H3 is reported. The iminoacyl ligand is η2-coordinated at the metal (TiC 2.096(4), TiN 2.149(4) A). The cyclopentadienyl ligands show the normal bent Cp2Ti structure.

Synthesis, complexation behaviour and reactions of thia-crown ethers incorporating propan-2-one units

Thia-crown ethers containing ketone functionality derived from 1,3-dichloroacetone have been prepared in 70–80% yields; the crystal structures of one free macrocycle and two AgI complexes have been determined.

Functionalized thia-crown ethers. Synthesis, structure, and properties

A caesium promoted synthesis of this-crown ethers containing isobutenyl units in the periphery is described, including structural data and a method involving diborane for functionalization of the methylene group.

Zinc chloride induced stereoselection in syntheses of α-amino-β-hydroxy acid derivatives

Schiff bases formed from condensation of glycine esters with diphenylmethyleneamine have been silylated followed by condensation with aliphatic and aromatic aldehydes at room temperature in the presence of catalytic amounts of ZnCl2; the syn-condensation products are obtained in good yield and stereoselectivity, especially for aromatic aldehydes, and the sense of Stereoselection reverses in the presence of stoichiometric or excess of ZnCl2.

Structures of a pair of diastereomeric salts of ephedrine and fluoro-substituted cyclic phosphoric acid

(1) (R)-(+)-4-(2,6-Dichlorophenyl)-2-hydroxy-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-oxide (1S,2R)-(-)-alpha-[(1-methylamino)ethyl]benzyl alcohol, (-)-C10H16NO+.(+)-C11H12Cl2O4P-, M(r) = 476.335, monoclinic, P2(1), a = 10.063(1), b = 8.206(1), c = 14.856(1) angstrom, beta = 104.84(1)-degrees, V = 1185.8 (2) angstrom3, Z = 2, D(x) = 1.334 Mg m-3, Mo K-alpha radiation (graphite monochromator), lambda = 0.71073 angstrom, mu(Mo K-alpha) = 0.3689 mm-1, F(000) = 500, T = 130 K, final R = 0.053, wR = 0.056 for 3504 observed unique reflections and 281 variables. (2) (S)-(-)-4-(2,6-Dichlorophenyl)-2-hydroxy-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-oxide (1R,2S)-(-)-alpha-[(1-methylamino)ethyl]benzyl alcohol hydrate, (-)-C10H16NO+.(-)-C11H12Cl2O4P-.H2O, M(r) = 494.351, orthorhombic, P2(1)2(1)2(1), a = 6.502(1), b = 11.393 (1), c = 32.739 (1) angstrom, V = 2425.2 (4) angstrom3, Z = 4, D(x) = 1.354 Mg m-3, Mo K-alpha radiation (graphite monochromator), lambda = 0.71073 angstrom, mu-(Mo K-alpha) = 0.3660 mm-1, F(000) = 1040, T = 130 K, final R = 0.055, wR = 0.059 for 4225 observed unique reflections and 265 variables. For both (1) and (2), the phosphorinane ring is in the usual chair conformation and the ephedrine is in an extended form. The crystal packing of (1) can be regarded as chains parallel to the b axis consisting of phosphorinane anions and ephedrine cations linked by hydrogen bonds. In the crystal packing of (2), which can also be regarded as chains parallel to the b axis, the solvent water molecules are incorporated in the hydrogen-bonding pattern between the phosphorinane and ephedrine ions.