bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and properties of linear, branched, and cyclic metallacarborane oligomers
Authors: Grimes Russell N. 
Published: October 2007

Abstract
A rapidly developing area of organometallic chemistry centers on polynuclear metal coordination compounds having specified, highly symmetric geometries such as squares, triangles, rectangles, or rigid rods. Interest in such molecules arises in part from their unusual, aesthetically appealing structures, and on the possibilities for assembling them into extended systems having useful electronic, optical, magnetic, catalytic, or other properties. Given their characteristic thermal and oxidative stability, chemical versatility, and relatively low-bulk, metallocene-like steric requirements, small metallacarboranes are attractive candidates as building blocks for such structures. Recent work in our laboratory on the controlled substitution and linkage of these clusters has opened the way to some new metallacarborane “designer ”chemistry that is described in this article.
Recent advances in the chemistry of carboranes and metallacarboranes
Authors: Hosmane Narayan S. 
Published: October 2007

Abstract
An overview of the syntheses, structures, and reactivity of the compounds formed by the incorporation of a number of d- and f-block metals into C2B4- and C2B9-carborane cages have been presented. In addition,the development of a safe, bench-scale preparation of the toxic and commercially unavailable polyhedral borane synthon, namely pentaborane(9), has also been described. Thus, this report discusses the latest developments leading to a sys- tematic synthetic approach to a number of carborane precursors and the subsequent reaction chemistry in the formation of a number of “carbons-apart ”metallacarboranes.
Use of organoboron halides in organic synthesis
Authors: Kabalka G. W. , Wu Z. , Ju Y. 
Published: October 2007

Abstract
Several new organic transformations have been achieved utilizing boron halide reagents. Aryl aldehydes are conveniently converted to gem-dichloromethylbenzenes using boron trichloride. Aryl aldehydes are alkylated by alkylboron chlorides in a Grignard-like fashion to generate the corresponding arylalkanols or alkylboron chlorides. Aryl aldehydes react with divinylboron halides (generated via the haloboration of alkynes) to produce 1,5-di-halo-1,4-dienes in excellent yields.
Polyhedral boron-containing cluster chemistry: Aspects of architecture beyond the icosahedron
Authors: Shea Suzanne L. , Bould Jonathan , Londesborough Michael G. S. , Perera Sarath D. , Franken Andreas , Ormsby Daniel L. , Jelínek Tomás , Stíbr Bohumil , Holub Josef , Kilner Colin A. , Thornton-Pett Mark , Kennedy John D. 
Published: October 2007

Abstract
For the structural extent of the polyhedral molecular chemistry of boron to rival that of the organic chemistry of the carbon hydrides, (a) the individual boron-containing polyhedra need to be fused together to make larger contiguous covalent assemblies, and (b) an intermolecular chemistry needs to be developed. Contemporary examples are given that illustrate novel chemistry in both these areas and that may point the way to some future developments.
New asymmetric syntheses with boronic esters and fluoroboranes
Authors: Matteson Donald S. 
Published: October 2007

Abstract
Efficient cleavage of sterically hindered boronic esters of asymmetric diols to recover both the diol and a more reactive borane derivative has been a challenging problem. A remarkable borosilicate glass-catalyzed cleavage with thionyl chloride and imidazole proved less useful than hoped for. Potassium bifluoride converts boronic esters to diols and alkyltrifluoroborates. These with chlorosilanes yield alkyldifluoroboranes, which with alkyl azides form secondary amines in high enantiopurity.
Mechanism of the opening of the closo-NB11 clusters by bases
Authors: Paetzold Peter , Müller Jens , Meyer Franc , Lomme Petra 
Published: October 2007

Abstract
The icosahedral aza-closo-dodecaboranes RNB11H11(R = H, Me, Ph) are opened by neutral bases L or anionic bases X– to give the nido-species RNB11H11L or [RNB11H11X]–, respectively, with a nonplanar pentagonal aperture; the N atom and a BHB hydrogen bridge are situated at opposite sides of the aperture. The BL or the BX vertex is found in the aperture either adjacent to the hydrogen bridge (type 1; C1) or adjacent to nitrogen (type 2;C1) or off the aperture adjacent to nitrogen on a mirror plane (type 3;Cs). At any rate, the isomer of type 1 is the primary product, which may rearrange to yield an isomer of type 3 via an isomer of type 2. Working in deuteromethanol shows that the bridging H atom originates from the primarily attacked BH vertex. The process from RNB11H11 to its base adduct of type 3 includes the opening and the closure of skeletal BN bonds and the jumping of the extra-H atom from endo into bridging positions and vice versa, whereas the base does not alter its position. The application of the opening process to a series of aza-closo-dodecaboranes with non-hydrogen boron ligands confirms that only atoms of the ortho-belt of the starting material are involved in structural changes. The elementary steps from the closo -species to the three isomers are identified as a [3c, 1c] collocation and subsequent [3c, 2c] translocations in the picture of molecular orbitals localized over three or two centers or to one center (lone pair).
Tandem allylboration-ring-closing metathesis reactions for the preparation of biologically active molecules
Authors: Ramachandran P. Veeraraghavan , Reddy M. Venkat Ram , Brown Herbert C. 
Published: October 2007

Abstract
The development of asymmetric synthesis during the past two decades aided organic chemists considerably in the synthesis of complex natural products. Organoborane chemistry continues to play an important role in asymmetric synthesis. One of the important reactions that has become very common in the arsenal of synthetic chemists is allylboration and related reactions. Another important reaction that has recently attained enormous importance in organic chemistry is the ring-closing metathesis (RCM) reaction. Indeed, a combination of allylboration and RCM reactions provides an excellent route to cyclic ethers, lactones, lactams, etc. Herein, we describe a sequential asymmetric allylboration and RCM reaction protocol that has been utilized for the synthesis of several alpha-pyrone-containing natural products,particularly biologically active molecules.
Small boranes, carboranes, and heterocarboranes
Authors: Siebert W. , Maier C.-J. , Maier A. , Greiwe P. , Bayer M. J. , Hofmann M. , Pritzkow H. 
Published: October 2007

Abstract
Dehalogenation of 1,2-dichloro-diborane(4) derivatives with Na/K alloy does not lead to planar cyclo-tetraboranes but to the blue puckered diisopropylamino compound and to the yellow 2,2,6,6-tetramethylpiperidino-tetraboratetrahedrane derivative, respectively. With smaller dialkylamino substituents, the formation of orange-red cyclo-hexaborane (BNMe2)6 and the green closo -hexaborane (BNEt2)6 is observed. When a 1:1 mixture of Me2NBCl2 and [Me2N(Cl)B]2 is dehalogenated, a small amount of colorless crystals of the planar diamond-shaped tetrabora-bicyclo-butane [(Me2N)2BB -BNMe2]2 is obtained. Its MO analysis reveals that eight framework electrons are used to form two 3c,2e sigma bonds, one 4c,2e pi bond, and one 4c,2e sigma bond along the edges.
A new approach to reactive closo-dicarbapentaboranes involves the hydroboration of dichloroboryl-tbutylacetylene with HBCl2 leading to Me3CCH2C(BCl2)3. On heating, it is transformed into the closo-dicarbapentaborane (Me3CCH2C)2(BCl)3, in which the chlorine atoms may be substituted to give new derivatives.
By reacting B2Cl4 with C5Me5-SiMe3 the nido-1-borane-2,3,4,5,6-pentacarbahexa- borane(6)is stabilized by the Lewis acid BCl3 to give (MeC)5B-BCl3.
Hydroboration of 3,4-bis(isopropylidene)-1,3-diborolanes leads to the formation of nido-2,3,5-tricarbahexaboranes(7),which may be deprotonated to give the corresponding anions isolobal with C5H5
-. Heterotricarbahexaboranes are obtained when a 3,4-bis(dichloroboryl)-2,5-hexadiene derivative is reacted with heptamethyldisilazane and hexamethyl-disilthiane to give the corresponding 1,2,5-azadiborolane and thiadiborolane. Their hydroboration leads to the aza-and thia-nido-dicarbahexaboranes, respectively.
Molecular and polymeric precursors to boron carbide nanofibers, nanocylinders, and nanoporous ceramics
Authors: Pender Mark J. , Forsthoefel Kersten M. , Sneddon Larry G. 
Published: October 2007

Abstract
New decaborane-based, single-source molecular and polymeric precursors to boron carbide have been developed that enable the formation of boron carbide in processed forms, including nanofibers, nanocylinders, and nanoporous materials.
New carboranes and phosphaboranes
Authors: Stíbr Bohumil 
Published: October 2007

Abstract
A review is presented on the new routes to the synthesis of the monocarbaboranes [arachno-6-CB9H14]–, arachno-4-CB8H14, and nido-1-CB8H12, that now have become excellent starting materials for the preparation of a family of seven-, eight-, and nine-vertex closo-monocarbaborane anions [2-CB6H7]–, [1-CB7H8]–, and [4-CB8H9]–. These anions exhibit high stability and have a good chance to become new candidates for weakly coordinated anion chemistry. Discussed are also reactions leading new families of phosphacarboranes that contain one, two, and three phosphorus atoms in the cage. These compounds, namely closo- 2,1-PCB8H9, closo-6,1-PCB8H9, nido -7,8,9-PC2B8H11, nido-7,8,11-PC 2B8H11, and nido- 7,8,9,10-P3CB7H8 ,are structural analogs of the corresponding carboranes and are likely to exhibit similar chemical behavior.
Boron clusters: Do they receive the deserved interest?
Authors: Teixidor Francesc , Viñas Clara , Demonceau Albert , Nuñez Rosario 
Published: October 2007

Abstract
New applications in which the carborane and metallacarborane species play a crucial role have been recently developed. In these applications, clusters display many particular characteristics that do not find parallel in their organic counterparts. The o-carborane can modulate the C···C distances depending on the substituents bonded to the cluster carbon atom and can lead to the formation of uncommon halogenophosphane charge-transfer “spoke ” complexes with iodine due to their electron-withdrawing capacity. Besides, metallacarboranes have been used as doping agents in organic conducting polymers and as catalysts in Kharasch reactions.
Supraicosahedral (metalla) carboranes
Authors: Boyd Alan S. F. , Burke Anthony , Ellis David , Ferrer Daniel , Giles Barry T. , Laguna Miguel A. , McIntosh Ruaraidh , Macgregor Stuart A. , Ormsby Daniel L. , Rosair Georgina M. , Schmidt Frank , Wilson Neil M. M. , Welch Alan J. 
Published: October 2007

Abstract
Although supraicosahedral (hetero) boranes have long been of interest to theoreticians, the area is under-developed from a synthetic viewpoint. The synthesis of supraicosahedral carboranes by reduction then capitation (RedCap) of C2B10 species is attractive, but unsuccessful as long as the cage carbon atoms are free to separate in the reduction step. Studies on 4,1,6-MC2B10 13-vertex metallacarboranes have shown that the partial degradation of such species can be a facile process, in spite of the fact that the binding energy of the metal atom to the carborane framework can be at least as high as that of a {BH}fragment. These findings support the general concept of the kinetic instability of 1,6-C2B11 species, explaining why a supraicosahedral carborane could not be made from 1,2-C2B10H12. However, tethering together the two cage C atoms with a C6H4(CH2)2 strap ultimately allowed the synthesis of the first supraicosahedral carborane. This species has a henicosahedral geometry, and there is evidence that a facile rearrangement from kinetic to thermodynamic isomer has occurred. The RedCap synthesis of this unprecedented cluster has the potential to be applied successively, yielding 14-,15-,16-, etc. vertex carboranes, the larger of which may be sufficiently kinetically stable to exist without a C,C tether.
Controlled synthesis of carbons-adjacent and-apart nido -and arachno-carborane anions and their metal complexes
Authors: Xie Zuowei 
Published: October 2007

Abstract
The controlled synthesis of carborane anions is a difficult challenge and is of great interest to synthetic chemists. By varying the bridge length of cage carbons-linked o-carboranes, the two cage carbon atoms are locked in place during the reactions, leading to the controlled synthesis of ortho-, meta- and para-isomer of nido-carborane dianions. The isomers of arachno-carborane tetraanions can also be prepared in the controlled manner via chang- ing the electronic configuration of the transition-metal ions or the bridge length. This article provides an overview of our recent work on this subject.
Boron-gadolinium binary system as a magnetic resonance imaging boron carrier
Authors: Yamamoto Yoshinori 
Published: October 2007

Abstract
The evaluation of the Gd-carborane DTPA complex as a magnetic resonance imaging (MRI) and boron carrier agent was carried out in vivo. The MRI revealed that the Gd-carborane DTPA was metabolized slower in the body in comparison with Gd-DTPA.
Enolboration of conjugated ketones and synthesis of beta-amino alcohols and boronated alpha-amino acids
Authors: Zaidlewicz M. , Sokól W. , Wolan A. , Cytarska J. , Tafelska-Kaczmarek A. , Dzielendziak A. , Prewysz-Kwinto A. 
Published: October 2007

Abstract
Enolization–aldolization of conjugated ketones, enantioselective synthesis of benzofuryl beta-amino alcohols, and synthesis of p-dihydroxyborylphenylalanine (BPA) and its analogs are described. Aldolization of benzaldehyde with lithium dienolates derived from unhindered conjugated cyclohexenones favored anti- selectivity, whereas syn selectivity was favored for hindered cyclohexenones. Anti-aldols were preferentially formed from dienolborinates derived from conjugated cyklohexenones, however,competing aldolization at the 2-position was observed for hindered ketones. Benzofuryl beta-amino alcohols were prepared using as a key step the enantioselective reduction of the corresponding alpha-bromoacetylbenzofurans with (–)-B- -chlorodiisopinocampheylborane. Ionic liquids were used as solvents for the synthesis of BPA by the Suzuki cross-coupling reaction. The reaction time is short, and a solution of the catalyst in the ionic liquid can be recycled.
Transcriptional roles of AhR in expression of biological effects induced by endocrine disruptors
Authors: Fujii-Kuriyama Yoshiaki , Mimura J. 
Published: October 2007

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), one of most toxic man-made chemicals, binds arylhydrocarbon receptor (AhR or dioxin receptor), whose endogenous ligand remains unknown, with an extremely high affinity and expresses pleiotropic biological effects. From analysis of the primary structures, AhR belongs to a distinct group of a super-gene family from that of nuclear receptors. PCB, 3-methylcholanthrene, and benzo(a)pyrene are also ligands to the AhR, and these polycyclic aromatic chemicals are considered to display pleiotropic biological effects such as induction of a variety of drug-metabolizing enzymes, teratogenesis, tumor promotion, immunodeficiency due to thymic involution, and liver damage. Generation of the AhR-deficient mice by gene knock-out technology revealed that these biological effects described are mediated by AhR, because AhR(-/-) mice lost susceptibility to these effects by TCDD and benzo(a) pyrene. It has recently been revealed that AhR is also involved in reproduction of female mice. Although the detailed mechanisms of involvement of AhR in exerting these effects are not always clarified, AhR is generally considered to function as a transcription factor, which activates the expression of genes by binding directly the XRE sequence in their promoter in a heterodimer form with Arnt. From analysis of DNA transfection and GST pull-down assays, it is revealed that AhR and Arnt interact with various coactivators such as RIP140, SRC-1/NcoA, and CBP/p300 to transmit their transactivation activity to general transcription factors (GTFs). AhR has also been shown to interact with various regulatory factors including Rb, NF-κB, and SP1, resulting in mutual inhibition or synergistic enhancement of their activities depending on the mode of localization of their cognate binding sequences in the target genes. Agonistic and antagonistic properties of various ligands to AhR also are discussed.
Nonmammalian nuclear receptors: Evolution and endocrine disruption
Authors: Thornton J. W. 
Published: October 2007

Most research to identify endocrine-disrupting chemicals and their impacts has relied on mammalian models or in vitro systems derived from them. But nuclear receptors (NRs), the proteins that transduce hydrophobic hormonal signals and are major mediators of endocrine disruption, emerged early in animal evolution and now play biologically essential roles throughout the Metazoa. Nonmammalian vertebrates and invertebrates, many of which are of considerable ecological, economic, and cultural importance, are therefore potentially subject to endocrine disruption by synthetic environmental pollutants. Are methods that rely solely on mammalian models adequate to predict or detect all chemicals that may disrupt NR signaling? Regulation of NRs by small hydrophobic molecules is ancient and evolutionarily labile. Within and across genomes, the NR superfamily is very diverse, due to many lineage-specific gene and genome duplications followed by independent divergence. Receptors in nonmammalian species have in many cases evolved unique molecular and organismal functions that cannot be predicted from those of their mammalian orthologs. Endocrine disruption is therefore likely to occur throughout the metazoan kingdom, and a significant number of the thousands of synthetic chemicals now in production may disrupt NR signaling in one or more nonmammalian taxa. Many of these endocrine disruptors will not be detected by current regulatory/scientific protocols, which should be reformulated to take account of the diversity and complexity of the NR gene family.
Concentration of phytohormones in food and feed and their impact on the human exposure
Authors: Verger Ph. , LeBlanc J. C. 
Published: October 2007

Phytohormones, which naturally occur in plants, must be taken into consideration for their contribution to the total human exposure to potential endocrine active substances (EASs). Phytohormones are usually divided into two families: phytoestrogens that are mainly occur from soybeans and soy derivatives and phytosterols that occur from vegetables and vegetable oils. The present paper compiles different sources of information about the concentration of phytohormones in foodstuffs in order to assess the current human exposure to those substances via food. A particular attention is given to most exposed groups of consumers, on the one hand, infants and young children fed with soy-based infant formulas for their exposure to phytoestrogens and on the other hand, consumers of fortified foods for their exposure to phytosterols. Available literature shows that the total dietary intake of isoflavones could reach 20 to 25 mg/day/person for the Japanese adult population. For infants and young children, the quantity of phytoestrogen ingested is likely to be 35-50 mg/day/person corresponding on a body weight basis to an exposure 7 to 11 times higher. Regarding phytosterols, an assessment of the exposure via food was done, considering both their natural occurrence and their potential concentration in fortified foods. Results shows that the "natural" exposure is estimated at 340 ± 440 mg/day/person at the mean and at 1040 mg/day/person at the 95th percentile. Considering the potential exposure via fortified foods, it is estimated at 2700 ± 1200 mg/day/person at the mean and at 4700 mg/day/person at the 95th percentile. After their ingestion, isoflavones are absorbed from the intestinal tract before being excreted in the urine and feces. The increasing use of phytohormones in human foodstuffs could increase locally their release into the environment. Nevertheless, considering the weak estrogenic potential of phytohormones in relation to synthetic or endogenous steroids, any introduction of these substances into aquatic ecosystems would probably have comparatively minor effects on aquatic organisms.
Pharmaceuticals and personal care products - A source of endocrine disruption in the environment?
Authors: Ingerslev F. , Vaclavik E. , Halling-Sørensen B. 
Published: October 2007

A wide variety of chemicals are used in pharmaceuticals. Most of these are already under thorough control for endocrine activity. The main causal agents recognized for endocrine disruption from sewage are substances used in medicine (sex hormones, glucocorticoids, and others), natural substances (estrone and 17β-estradiol), and synthetic estrogens (e.g., 17α-ethinylestradiol). Similar substances are used in anabolic agents (growth hormones) in livestock production in some countries. Although the estimated use of anabolic agents in livestock production is approximately one order of magnitude below the natural release of estrogens from farm animals, their possible significance remains unanswered. At present, no other medical substances are recognized as endocrine disruptors in the environment. However, candidates may be identified on the basis of simple assumptions regarding their use and activity: (1) Nonestrogenic steroids may react with environmental endocrine receptors or metabolize on their way to the environment and thus form endocrine disruptors. (2) Many high-volume drugs released to the environment have not yet been tested for their endocrine properties, and some of these are known to interact with the human endocrine system. (3) Compared to medicinal substances, personal care products and additives in drugs are used in high amounts; from this group, parabens, siloxanes, and other substances are suspected of causing endocrine disruption in the environment.