Tame Combings of Groups

In this paper, we introduce the idea of tame combings for finitely presented groups. If is a closed irreducible 3-manifold and is tame combable, then the universal cover of is homeomorphic to . We show that all asynchronously automatic and all semihyperbolic groups are tame combable.

     

1-[Ferrocenyl(hydroxy)methyl]-1,7-dicarba<Emphasis Type="Italic">-closo</Emphasis>-dodecaborane: Synthesis and X-ray crystal structure

The synthesis and molecular structure of the novel 1-[ferrocenyl(hydroxy)methyl]-1,7-dicarba-closo-dodecaborane (1) is described. Compound 1 was synthesized from reaction of m-carborane and ferrocene carboxaldehyde using n-butyllithium (n-BuLi) or tetrabutylammonium fluoride (TBAF) in THF in 45% and 36% yield, respectively. Compound 1 consists of a ferrocene molecule tethered to m-carborane through a methylhydroxy bridge. The crystal structure of 1 was determined by single crystal X-ray diffraction analysis. Crystal data: 1 [Fe(C₅H₅)(C₅H₄-CH₂O-1,7-C₂B₁₀H₁₂)], formula weight = 359.17, crystallized in orthorhombic system, space group Pna2 ₁ with a=19.698(4) ?, b=10.709(2) ?, c=8.520(2) ?, and V=1797.3(7) ?³ and Z=4. Refined to R ₁=0.043 for 4124 observed reflections with I/σ>2σ(I). The compound was crystallized as racemic twins in a ratio of 73(2)/27(2). The unsubstituted Cp ring was disordered and modeled as two conformations in a 53(3)/47(3) ratio. Intermolecular hydrogen bonding was observed from the hydrogen of the meta-carbon on the carborane cluster towards the hydroxyl oxygen.     

Caging the mercurous ion: a tetradentate tripodal nitrogen ligand enhances stability and J(1H199Hg)

The dimeric mercurous ion has been encapsulated by a pair of the tetradentate tripodal nitrogen ligands tris[(2-(6-methylpyridyl))methyl]amine (TLA). The complex [Hg₂(TLA)₂](ClO₄)₂ (1) was isolated directly from an acetonitrile solution of Hg(ClO₄)₂ 3H₂O and TLA. Complex 1 crystallizes in the triclinic space group with a = 10.537(2) Å, b = 10.751(2) Å, c = 10.907(2) Å, = 75.20(3), = 73.73(3), = 75.73(3), and Z = 1. The cation is located an inversion center. The Hg–Hg and Hg–N_amine bond distances are 2.5469(8) and 2.297(6) Å, respectively, and the average Hg–N_pyridyl bond length is 2.75(7) Å. Complex 1 was stable indefinitely in acetonitrile-d ₃ solution, permitting detection of 13 and 22 Hz heteronuclear couplings between the Hg(I) ions and the methylene protons of the ligand. Comparisons with the structures and spectroscopic properties of related mercuric and mercurous complexes are made.     

Magnesium nitride as a convenient source of ammonia: preparation of primary amides

The use of magnesium nitride (Mg 3N 2) as a convenient source of ammonia has been explored for the direct transformation of esters to primary amides. Methyl, ethyl, isopropyl, and tert-butyl esters are converted to the corresponding carboxamides in good yields (75-99%).     

Facile and general synthesis of quaternary 3-aminooxindoles

A novel approach to the valuable quaternary 3-aminooxindole skeleton is reported on the basis of intramolecular arylation of enolates of substituted amino acids. The reaction tolerates dialkyl- and arylalkylamines as well as a range of carbon substituents (primary and secondary alkyl, aryl). The cyclization of N-indolyl-substituted substrates is accompanied by direct C-H arylation of the indole, leading to indolo-fused benzodiazepines.     

Highly (E)-selective Wadsworth-Emmons reactions promoted by methylmagnesium bromide

An experimentally simple protocol for the very highly (E)-selective Wadsworth-Emmons reaction [(E):(Z) selectivities in excess of 180:1 in some cases] of a range of straight-chain and branched aliphatic, substituted aromatic, and base-sensitive aldehydes via reaction with an alkyl diethylphosphonoacetate and MeMgBr is reported.     

Synthesis of natural products from the Indian neem tree Azadirachta indica

The synthesis of five natural products (3, 6, 7, 10, and 14), isolated from the Indian neem tree Azadirachta indica, is reported from a common intermediate (2). The judicious choice of transacetalization conditions allows efficient access to both the azadirachtinin (9 and 10) and the azadirachtin (3, 6, 7, and 14) skeletons.     

'Lock and key' control of optical properties in a push-pull system

We report the modulation of the absorbance of a flavin push-pull derivative through specific recognition by a complementary diamidopyridine (DAP), shifting the flavin intramolecular charge transfer band by approximately 30 nm.     

Surface binding vs. sequestration; the uptake of benzohydroxamic acid at iron(iii) oxide surfaces

Benzohydroxamic acid is shown to be an unexpectedly good ligand for iron(iii) oxides, favouring surface attachment to the formation of trisbenzohydroxamato complexes, which are known to have very high thermodynamic stability in solution.     

Ring contracting sulfur extrusion from oxidized phenothiazine ring systems

Lithium, used in conjunction with sodium metal, produces a high yield of carbazole when reacted with phenothiazine-5-oxide or phenothiazine-5,5-dioxide. A high yield of 9-ethylcarbazole is also produced when these reagents react with 10-ethylphenothiazine, 10-ethylphenothiazine-5-oxide, and 10-ethylphenothiazine-5,5-dioxide. Degassed Raney nickel produces carbazole in high yield when reacted with phenothiazine and phenothiazine-5-oxide. A moderate yield of 9-ethylcarbazole is produced when n-butyllithium is reacted with 10-ethylphenothiazine-5-oxide.