Synthesis of Phosphorylated Derivatives of Sucrose: 6,6′-di-Phosphonate, 6- and 6′-Phosphonates,and 6,6′-di-Phosphine

Reaction of 6,6′dideoxy-6,6′di-iodo-1′,2,3,3′,4,4′-hexa-O-benzylsucrose with triethyl phosphite afforded the corresponding 6,6′-diphosphonate. Selective phosphonylation either at the C-6 or 6-6′ position was also possible providing the corresponding sucrose mono-phosphonates. Reaction of 6,6′-dichloro-hexa-O-benzylsucrose with diphenylphoshine anion afforded the 6,6′-diphosphinosucrose.     

6,6′-Dibromo-3,3′-dimethoxy-2,2′-dihydroxy-1,1′-biphenyl: preparation and resolution

A pratical route to prepare the title biphenyl 1 starting from 3,3′,2,2′-tetramethoxy-1,1′-biphenyl 2 is described. Resolution of 1 was achieved by its conversion into the corresponding diastereomeric menthyldicarbonate. The absolute configuration of (P)-(+)-1 was confirmed by X-ray analysis of the related diastereomer.     

Synthesis of cobalt and nickel 6,6′-diphenylbis(dicarbollides)

Russian Chemical Bulletin - 6,6′-Diphenyl derivatives of cobalt and nickel bis(dicarbollide) were synthesized starting from nido-carborane by the insertion—deboronation—insertion...     

The structure of 6,6′-biquinolyl and its dication in solution

Conformational analysis of 6,6-biquinolyl and its dication was performed using dipole moments and data from electric and magnetic birefringence. The rotation angles between the quinoline rings for thecis- andtrans-conformers in solution are 50°. The emergence of positive charges on both heteroaromatic rings does not result in noticeable changes in the spatial structure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 330–332, February, 1994.     

Isolation and Crystal Structure of Trans-2,2′,4,4′-tetramethyl-6,6′-dinitro Azobenzene

Trans-2,2′,4,4′-tetramethyl-6,6′-dinitro azobenzene (C16H16N4O4, Mr = 328.32) was isolated from benzene extract of the leaves of Aconitum sungpanense Hand. Mazz. as a new compound, and characterized by spectral methods and X-ray diffraction analysis. It crystallizes in monoclinic system, space group P21/c with a = 8.544(1), b = 13.997(2), c = 7.161(1) A, β = 112.97(1), V = 788.4(2)A3, Z = 4, Dc = 1.383 g/cm3, F(000) = 344 and μ(MoKα) = 0.102 mm-1. The final R = 0.0395 and wR = 0.1140 for 1913 independent reflections with Rint = 0.0109 and 1329 observed reflections with I > 2((I). The molecule is composed of two phenyl rings through trans N=N.     

Efficient Preparative Rentes to 6,6′-Dibromo-2-2′-bipyridine and 6-Bromo-2,2′-bipyridine

The preparation of 6,6′-dibromo-2,2′-bipyridine and 6-bromo-2,2′-bipyridine are described. The dibromo compound was prepared by way of an improved cuprate synthesis resulting in a 72% yield. The monobromo species was prepared from the dibromo compound by way of metal-halogen exchange in 88% yield.     

Spectroscopic and electrochemical properties of cyclopalladated complexes of 2,3-diphenylquinoxaline and 2,2′,3,3′-tetraphenyl-6,6′-biquinoline

Comparative study of cyclopalladated ethylenediamine complexes of 2,3-diphenylquinoxaline (Hdphqx) [Pd(dphqx)En]ClO₄ and 2,2′,3,3′-tetraphenylbiquinoline (H₂tphbq) [(PdEn)₂(μ-tphbq)](ClO₄)₂, and the free heterocyclic ligands was performed by means of ¹H NMR spectroscopy, electronic absorption and emission spectroscopy, and cyclic voltammetry. It was shown that cyclopalladation gives rise to a long-wave absorption band in the visible spectrum, a batochromic shift of the vibrationally structured phosphorescence band, and an anodic shift of the ligand-centered reduction potential of the complexes com-pared to free ligands.     

Helix-forming self-assembly of enantiopure 2,2′-dimethylbiphenyl-6,6′-dipropiolic acid and amide organized by hydrogen bonds

Single-crystal X-ray diffraction revealed that the molecules of both the title compounds (S)-5 and (S)-6 are linked, via double hydrogen bonds, in infinite chains which follow the crystallographic symmetry of the three- and four-fold screw axis, respectively. To our knowledge this represents the first documented case when intermolecular carboxylic hydrogen bond constitutes an integral part of a helix backbone set up from repeating homochiral subunits.     

2,2′-Bipyridine-6,6′-bis(carbothioamide) metal complexes

Complexes of 2,2-bipyridine-6,6-bis(carbothioamide), obtained with a variety of metal cations, were characterised by microanalyses, molar conductivities and by i.r. and n.m.r. (for diamagnetic compounds) spectra. The iron(II) complex was also characterised by Mössbauer spectroscopy. The spectral data indicate that, in all cases, the ligand coordinates to the metal through one pyridine nitrogen and one sulphur.     

Synthesis of 5,5′-Dialkyl-6,6′-dichloro-2, 2′-bipyridines

5,5′-Dialkyl-6,6′-dichloro-2,2′-bipyridines were synthesized starting from 3-substituted 2-chloro-6-iodopyridines using Pd-catalyzed coupling conditions. 6-Alkyl-3,5-dichloro-2H-1,4-oxazin-2-ones were excellent precursors for the synthesis of these functionalized 2-iodo-6-chloropyridines.     

6,6′-Dimethoxygossypol: molecular structure,crystal polymorphism,and solvate formation

6,6′-Dimethoxygossypol (DMG) is a naturally occurring derivative of gossypol that is found in relatively high concentration in some Gossypium barbadense cotton varieties. Like gossypol, DMG forms an equimolar solvate with acetic acid, but it was not known if, like gossypol, the compound would also form clathrates with other molecules. To test for this, the compound was crystallized from different solvents. Four new structures of DMG were found that include two polymorphic and two solvated forms. The polymorphs include two monoclinic structures with P2₁/c and C2/c space groups (P1 and P2, respectively). Packing of the DMG molecules P1 is similar to packing of the gossypol molecules in the P1 polymorphic form of gossypol. The DMG molecules in P2 pack in a highly ordered arrangement that has not been previously observed among gossypol structures. DMG forms equimolar solvates with water (S1) and cyclohexanone (S2). Both structures are triclinic with P [`1]P \bar {1} space groups. The DMG molecules in S2 assemble in a manner that is similar to the gossypol molecules of gossypol–cyclohexanone (1:1), and the DMG molecules in S1 pack in a manner that is similar to the DMG molecules in DMG–acetic acid (1:1) as well as the gossypol molecules in gossypol–acetic acid (1:1). Although DMG is not as versatile a host compound as gossypol, it still forms solvates under many crystallization conditions. Consequently, some care is needed to be sure that one understands exactly which form is recovered when the compound is isolated.     

Preparation and resolution of 2,2′-dimercapto-6,6′-dimethoxy-1,1′-biphenyl: a C2-symmetric sulfur building block

The preparation of the title dimercaptan 1 starting from 2,2′-dihydroxy-6,6′-dimethoxy-1,1′-biphenyl 2 is described. Resolution of dimercaptan 1 was performed using (−)-(1R,2S,5R)-menthyl chloroformate as a chiral resolving agent. The procedure affords dimercaptan (+)-1 and (−)-1 in 98% ee and 93% ee, respectively. A new and direct intermolecular Ullmann coupling resulting in an improved preparation of diol 2 is also reported.     

1,1′,2,2′,6,6′-Hexaphenyl-4,4′-bipyridinium cation radical

Aniline reacts with 2,2,6,6-tetraphenyl-4,4-bipyrilium perchlorate to form 1,1,2,2,6,6-hexaphenyl-4,4-bipyridine perchlorate. A relatively stable cation radical is formed in the first stage of electrochemical reduction of this compound, which has been examined by ESR, where there are splittings from two nitrogen nuclei and the four protons in the 3,3,5,5 positions: a_N=0.38; a_H=0.14 mT.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, No. 1, pp. 61–64, January–February 1992.     

Self-assembly of enantiopure 2,2′-dimethylbiphenyl-6,6′-dicarboxylic acid. Formation of chiral squares and their columnar stacking

The title (R)-diacid has been found to self-assemble as hydrogen-bonded cyclotetramers in solution as well as in the solid phase; in the crystal the tetramers are stacked into chiral columns. In contrast, the racemic diacid forms infinite zig-zag chains of molecules of alternating chirality.     

Crystal structure of 1,1′-biphenyl-2,2′,3,3′-tetracarboxylic and 1,1′-biphenyl-2,2′,3,3′,5,5′,6,6′-octacarboxylic acids: solid-state chiralization and dissociation

X-ray diffraction analysis revealed unexpected stereochemical features accompanying crystal self-assembly of the two title oligocarboxylic acids.     

Preparation of 6,6′—Bisperfluoroalkylated BINOLs and Their Application in Asymmetric Alkylation of Benzaldehyde

6，6′-Bis(1H,1H,2H,2H-perfluorooctyl)-BINOL and 6,6′-bis(1H,1H,2H,2H-perfluorodecyl)-BINOL were synthesized through Suzuki coupling reaction and used in fluorous biphase asymmetric alkylation of benzldehyde,Good enantioselectivity was obtained and the catalysts could be recovered by liquid-liq-uid extraction.     

2,2′-Diamino-6,6′-dimethylbiphenyl as an efficient ligand in the palladium-catalyzed Suzuki–Miyaura and Mizoroki–Heck reactions

2,2′-Diamino-6,6′-dimethylbiphenyl was found to be an efficient ligand in the palladium-catalyzed Suzuki–Miyaura coupling reactions of aryl iodides, bromides, and chlorides and Mizoroki–Heck reactions of aryl iodides and bromides. Under appropriate conditions, all reactions gave the desired products in moderate to excellent yields. The ligand is inexpensive, air-stable and easy to available.     

Synthesis and coordination chemistry of the tetradentate ligands 6,6′-bis(3-pyrazolyl)-2,2′-bipyridine and 6,6′-bis(2-hydroxyphenyl)-2,2′-bipyridine: intramolecular hydrogen-bonding in complexes of Cu(II), and a dinuclear double helicate with Ag(I)

Simple syntheses of the potentially tetradentate chelating ligands 6,6′-bis(3-pyrazolyl)-2,2′-bipyridine (H₂L¹), and 6,6′-bis(2-hydroxyphenyl)-2,2′-bipyridine (H₂L²) are described: H₂L¹ is a new ligand, whereas H₂L² is known, but investigation of its coordination chemistry has been hampered by the lack of a simple synthesis. Complexes of both have been structurally characterised and reveal many interesting features. [Cu(HL¹)(H₂O)][PF₆] is square pyramidal with an axial H₂O ligand, but, in the solid state, forms a hydrogen-bonded dimer in which the peripheral pyrazolyl groups of HL¹ (one protonated, one deprotonated) in one complex unit form a two-point ‘chelating’ hydrogen-bonding interaction with the axial water ligand of the second, and vice versa. In contrast, [Ag₂(L¹)₂][BF₄]₂ is a dinuclear double helicate because of the preference of Ag(I) ions for a pseudo-tetrahedral geometry. [Cu(L²)] has a typical near-planar geometry with a N₂O₂ donor set, and monomeric units are associated into centrosymmetric dimers in the crystal via weak axial Cu⋯O(phenolate) interactions to give an asymmetric [Cu₂(μ-phenolate)₂] core. In {[Cu(L²)]₂H}(PF₆), the two monomeric [Cu(L²)] units are also associated via axial phenolate interactions to give a dimer with a [Cu₂(μ-phenolate)₂] core, but, in addition, the extra proton per dimer unit is located at the centre of a short, strong O⋯H⋯O hydrogen-bond that links a phenolate group from each of the two monomer units. The geometry of dimer formation is changed in order to allow the phenolate groups to approach one another closely enough for this hydrogen-bond to form.     

Thermal conductivity behavior of SiC–Nylon 6,6 and hBN–Nylon 6,6 composites

A study was performed to determine the effect of the content and orientation of fillers on the thermal conductivity of a polymeric composite packed with hexagonal boron nitride (hBN) and silicon carbide (SiC) fillers. The thermal conductivity behavior of SiC–Nylon 6,6 and hBN–Nylon 6,6 composites was more dependent on the orientation and shape of the filler than on its thermal conductivity. The thermal conductivity of SiC–Nylon 6,6 composites with 59 % (v/v) isotropic SiC fillers increased from 0.25 to 3.83 W/m K. That of hBN–Nylon 6,6 composites with 62 % (v/v) anisotropic hBN fillers increased from 0.25 to 2.16 W/m K in the perpendicular direction whereas in the parallel direction it increased rapidly to 8.55 W/m K .