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Query: UNIPROT:Q86TM3 (cage)
 29,987 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Framework-substituted, molecular-sieve, aluminophosphate, microporous solids are the centerpieces of a new approach to the aerobic oxyfunctionalization of saturated hydrocarbons. The sieves, and the few percent of the Al(III) sites within them that are replaced by catalytically active, transition-metal ions in high oxidation states (Co(III), Mn(III), Fe(III)), are designed so as to allow free access of oxygen in to and out of the interior of these high-area solids. Certain metal-substituted, molecular sieves permit only end-on approach of linear alkanes to the active centers, thereby favoring enhanced reactivity of the terminal methyl groups. By optimizing cage dimension, with respect to that of the hydrocarbon reactant, as well as adjusting the average separation of active centers within a cage, and by choosing the sieve with the appropriate pore aperture, highly selective conversions such as n-hexane to hexanoic acid or adipic acid, and cyclohexane to cyclohexanol, cyclohexanone, or adipic acid, may be effected at low temperature, heterogeneously in air.
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PMID:Molecular sieve catalysts for the regioselective and shape- selective oxyfunctionalization of alkanes in air. 1126 77

The complex Co4 1(2)8- is a tetranuclear cobalt(II) cage compound that assembles in aqueous solutions above pH 4 and is capable of encapsulating a variety of organic guest molecules, for example, benzene, hexane, chlorobutane, butanol, and ethyl acetate. Ligand 1 is a resorc[4]arene-based molecule with iminodiacetate moieties appended to its upper rim. 1H NMR studies of Co4 1(2)8-.guest complexes demonstrate inclusion of nonpolar hydrocarbons, substituted phenyls, alcohols, halogen-containing hydrocarbons, and polar organic molecules. The complex Co4 1(2)8- acts as an NMR shift reagent and causes substantial upfield isotropic hydrogen shifts (-30 to -40 ppm) in the guest molecule and separation of the guest hydrogen chemical shifts by typically 12 ppm. The complex Co4 1(2)8- will encapsulate molecules with fewer than eight atoms in a linear chain, mono- and disubstituted benzenes, and polar molecules with greater than two carbon atoms. The solid-state structure of Ba4[Co4 1(2).C6H5C2H5] shows a disordered guest molecule encapsulated within the cavity of Co4 1(2)8-. The cavity dimensions, bond lengths, and bond angles of Ba4[Co4 1(2).C6H5C2H5] are very similar to those determined in Ba4[Co4 1(2).6H2O].
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PMID:Metal-assembled cobalt(II) resorc[4]arene-based cage molecules that reversibly capture organic molecules from water and act as NMR shift reagents. 1127 77

Boron-10 enriched boric acid, H310BO3, was converted to the corresponding sodium borohydride, Na10BH4, in essentially quantitative yields, by using slightly modified literature methods involving the formation of butyl borate, (n-OBu)310B, first and then reacting it with NaH in mineral oil. The oxidation reaction of Na10BH4 with I2 in diglyme and subsequent addition/purification in dioxane gave Na[10B3H8]0.3(C4H8O2) that reacted further with NiCl2 in either anhydrous benzene or heavy mineral oil at 110 degrees C to produce the corresponding 10B5H9 as the first isolated 10B-enriched liquid boron hydride in a laboratory environment. Treatment of this 10B5H9 with NaH or t-BuLi in 2:1 molar ratio underwent a cage expansion reaction to produce the [M]10B9H14 that undergoes a redox reaction in situ with anhydrous NiCl2 in n-hexane to yield the corresponding fused cage anti-10B18H22 as the only solid borane product in 42% yield, thus establishing new synthetic routes for the preparation of 10B-enriched polyhedral boranes.
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PMID:A new synthetic route to boron-10 enriched pentaborane(9) from boric acid and its conversion to anti-(10)B(18)H(22). 1207 37

The translational and rotational dynamics of n-hexane adsorbed in ZSM-5 and 5A zeolites has been studied by neutron scattering and deuterium solid-state NMR, at various temperatures. The dynamics of n-hexane is quite different in the two zeolites. In the ZSM-5 structure, the molecule sits in channel segments, the energy barrier between adjacent adsorption sites is small and fast anisotropic motions are observed. In the 5A zeolite, the molecule is adsorbed in alpha-cages; the barrier between adjacent cages is larger so that the molecule spends a longer time exploring the volume of an alpha-cage, leading to a more isotropic motion. The diffusion coefficient of the molecule is reduced by more than 4 orders of magnitude in 5A zeolite compared with ZSM-5.
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PMID:Comparison of the dynamics of n-hexane in ZSM-5 and 5A zeolite structures. 1500 80

[reaction: see text] The regio- and stereochemistries of photo-Claisen reactions of 1-naphthyl (R)-1-phenylethyl ether ((R)-2), in combination with photo-Fries and photo-Claisen-type reactions of 1-naphthyl (R)-2-phenylpropanoate ((R)-1), have been investigated in n-alkanes of different viscosities and at several temperatures. Analyses of the results provide detailed information about the in-cage motions of the singlet prochiral 1-naphthoxy/1-phenylethyl radical pairs (radical-pair B) that are formed directly from (R)-2 and indirectly from (R)-1 via decarbonylation of singlet chiral 1-naphthoxy/2-phenylpropanoyl radical pairs (radical-pair A). In hexane at 23 degrees C, the photo-Claisen products from irradiations of (R)-2 retain up to 31% enantiomeric excess (ee), but the ees of the same photoproducts from (R)-1 are near 0%. This disparity is attributed to differences between the initial orientations of the constituent radicals of radical-pair B at the moment of their "birth". The regio- and stereoselectivities reach plateau values as the solvent viscosity increases, indicating that the relationships between the rates of radical-radical bond formation and either translational or tumbling motions within a solvent cage reach an asymptotic limit. Detailed analyses are presented of the various motions that are in competition within a solvent cage during the very short lifetimes of the radical pairs. The data, in toto, present interesting insights into how radical pairs move during short periods and over short distances when their solvent cages have walls of varying flexibility.
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PMID:Analyses of in-cage singlet radical-pair motions from irradiations of 1-naphthyl (R)-1-phenylethyl ether and 1-naphthyl -2-phenylpropanoate in n-alkanes. 1570 57

Photo-Fries rearrangements of 4-dodecylphenyl phenylacetate have been investigated in polyethylene films with 0-71% crystallinity and in hexane over a range of temperatures. The results are compared to those reported previously from phenyl phenylacetate and 1-naphthyl tetradecanoate to assess the influence of a long alkyl chain on the in-cage motions of the intermediate singlet radical pairs. It is demonstrated that the reactivity and selectivity of intimate singlet radical pairs can be tuned by judicious placement of long-chain substituents and selection of a specific polyethylene type as the reaction matrix.
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PMID:Comparisons of photo-fries rearrangements of 4-dodecylphenyl phenylacetate and two structurally related esters in hexane and polyethylene cages. How important are anchoring chains? 1603 80

Redox transmetallation/ligand exchange reactions of lanthanoid metals (Ln), Hg(C6F5)2 and HOAr(OMe) (Ar(OMe) = C6H2-2,6-Bu(t)-4-OMe), in thf (tetrahydrofuran) gave, for Ln = Yb, [Yb(OAr(OMe))2(thf)3], and for Ln = Sm, a mixture of [Sm(II)(OAr(OMe))2(thf)3] and mainly [Sm(III)(Ar(OMe))3(thf)] x thf. X-Ray structure determinations show the divalent complexes to have distorted square-pyramidal stereochemistry with transoid thf and OAr(OMe) ligands in the basal plane. Treatment of [Yb(OAr(OMe))2(thf)3] with diethyl ether or PhMe at room temperature gave [Yb(OAr(OMe))2] or [Yb(OAr(OMe))2] x 0.5 PhMe. For lanthanoids Ln = Nd, Er or Y, the reactions with Hg(C6F5)2 and HOAr(OMe) yielded complex product mixtures, from one of which the novel erbium aryloxide fluoride cage [Er3(OAr(OMe))4(mu2-F)3(mu3-F)2(thf)4] x thf x 0.5 C6H14 was isolated. The cage core consists of a triangle of Er atoms joined to two mu3-fluoride ligands and three further mu2-fluorides bridge adjacent Er atoms. One of the Er atoms is six-coordinate with additionally two OAr(OMe) ligands whilst the other two have one OAr(OMe) and two thf ligands and are seven coordinate. Substitution of Hg(C6F5)2 by Hg(CCPh)2 in the redox transmetallation/ligand exchange reactions gave the new derivatives [Ln(OAr(OMe))3(thf)] x thf (Ln = La, Pr, Nd, Sm, Gd, Ho) in good yields whilst Ln = Yb gave [Yb(OAr(OMe))2(thf)3]. Recrystallisation of [Sm(OAr(OMe))3(thf)] x thf from dme (1,2-dimethoxyethane) yielded [Sm(OAr(OMe))3(dme)]. Structural characterisation of [Ln(OAr(OMe))3(thf)] x thf (Ln = Nd, Ho) and [Sm(OAr(OMe))3(dme)] showed monomeric four-coordinate distorted tetrahedral and five-coordinate distorted square-pyramidal complexes respectively. For the smaller lanthanoids Ln = Y, Er or Lu, reactions with Hg(CCPh)2 and HOAr(OMe) gave the mixed aryloxide/alkynide complexes [Ln(OAr(OMe))2(CCPh)(thf)2]. Oxidation of the divalent ytterbium aryloxide [Yb(OAr(OMe))2(thf)3] by Hg(CCPh)2 in thf gave the analogous [Yb(OAr(OMe))2(CCPh)(thf)2]. The erbium alkynide [Er(OAr(OMe))2(CCPh)(thf)2] x 0.25 C6H14 has distorted square-pyramidal stereochemistry with transoid OAr(OMe) and thf ligands in the basal plane and a rare (for Ln) terminal alkynide ligand in the apical position. The reactive Lu-C bond in the [Lu(OAr(OMe))2(CCPh)(thf)2] complexes could be slowly cleaved by free HOAr(OMe) in hydrocarbon solvents, yielding Lu(OAr(OMe))3 species and fortuitous partial hydrolysis of [Er(Ar(OMe))2(CCPh)(thf)2] gave the dimeric [Er(OAr(OMe))2(mu-OH)2]2.
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PMID:Manipulation of reaction pathways in redox transmetallation-ligand exchange syntheses of lanthanoid(II)/(III) aryloxide complexes. 1643 75

The ayurvedic medicinal plant Gotukola (Centella asiatica) was evaluated for its anxiolytic properties. Specifically, this study assessed the effects of: Gotukola plant materials of different genotypic origin; hexane, ethyl acetate and methanol extracts of Gotukola; and asiaticoside, a triterpenic compound isolated from Gotukola. Various paradigms were used to assess the anxiolytic activity, including the elevated plus maze (EPM), open field, social interaction, locomotor activity, punished drinking (Vogel) and novel cage tests. The EPM test revealed that Gotukola, its methanol and ethyl acetate extracts as well as the pure asiaticoside, imparted anxiolytic activity. Furthermore, the asiaticoside did not affect locomotor activity, suggesting these compounds do not have sedative effects in rodents.
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PMID:Evaluation of anxiolytic properties of Gotukola--(Centella asiatica) extracts and asiaticoside in rat behavioral models. 1648 24

Both the regio- and stereo-chemistries of the photoreactions of 1-naphthyl (R)-2-phenylpropanoate have been investigated in poly(vinyl acetate) films in their glassy (at 5 degrees C) and melted (at 50 degrees C) states and in ethyl acetate. These results are compared with those from irradiations in polyethylene films and in n-hexane. The regioselectivity of the intermediate 1-naphthoxy/(R)-2-phenylpropanoyl radical pair combinations is much higher in both the melt and glassy states of poly(vinyl acetate) films than that in the melt state of completely amorphous polyethylene films, but the stereoselectivity of intermediate prochiral 1-naphthoxy/1-phenylethyl radical pair combinations is much lower in poly(vinyl acetate). The results emphasize the need to control the ratio between the rates of radical tumbling and translation, as well as the ratio between the rates of in-cage motions and cage-escape, if high stereo- and regio-selectivities of combination products are to be achieved. A mechanistic picture of how the radicals of the intermediate pairs are affected by and interact with the various media is advanced.
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PMID:Photo-Fries rearrangements of 1-naphthyl (R)-2-phenylpropanoate in poly(vinyl acetate) and ethyl acetate. Influence of medium polarity and polymer relaxation on motions of singlet radical pairs. 1653 5

This study seeks an answer to the following question: Is it possible to design a supramolecular cage that would "solvate" the excess electron in the same fashion in which several solvent molecules do that cooperatively in polar liquids? Two general strategies are outlined for this "electron encapsulation", viz. electron localization using polar groups arranged on the (i) inside of the cage or (ii) outside of the cage. The second approach is more convenient from the synthetic standpoint, but it is limited to polynitriles. We demonstrate, experimentally and theoretically, that this second approach faces a problem: the electron attaches to the nitrile groups, forming molecular anions with bent C-C-N fragments. Because the energy cost of this bending is high, for dinitrile anions in n-hexane, the binding energies for the electron are low and, for mononitriles, these binding energies are lower still, and the entropy of electron attachment is anomalously small. Density functional theory modeling of electron trapping by mononitriles in n-hexane suggests that the solute molecules substitute for the solvent molecules at the electron cavity, "solvating" the electron by their methyl groups. We argue that such species would be more correctly viewed as multimer radical anions in which the electron density is shared (mainly) between C 2p orbitals in the solute/solvent molecules, rather than cavity electrons. The way in which the excess electron density is shared by such molecules is similar to the way in which this sharing occurs in large di- and polynitrile anions, such as 1,2,4,5,7,8,10,11-octacyanocyclododecane(-). Only in this sense is the electron encapsulation possible. The work thus reveals limitations of the concept of "solvated electron" for organic liquids: it is impossible to draw a clear line between such species and a certain class of radical anions.
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PMID:Toward electron encapsulation: polynitrile approach. 1680 99


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