Lithium In Liquid Ammonia Research Articles

Hydroxyl Boron Nitrid e/Natural Rubber Composites with Enhanced Mechanical and Thermal Conduction Properties: Implications for Heat Dissipative Tires or Conveyor Belts

For its significant technological interest, a systematic investigation on mechanical and thermal conduction properties of natural rubber reinforced by functionalized hexagonal boron nitride nanosheets is highly desirable. We herein first demonstrate a unique synthesis of hydroxyl-functionalized boron nitride nanosheets (OH-BNNSs) via a simple one-pot reduction reaction. This involves negative charging by treating BNNSs with lithium in liquid ammonia and subsequent bubbling of oxygen into dispersion of BNNS salts. Subsequently, a series of functionalized boron nitride nanosheets/natural rubber (NR) composites were fabricated by latex mixing and co-coagulation. Co-coagulating a stable aqueous suspension of OH-BNNSs with natural rubber latex afforded a weblike morphology consisting of platelet networks between the latex particles. Compared to pure rubber, the tensile strength and storage modulus at 25 °C for OH-BNNSs/NR (5 wt %) are increased by 466% and 1 order of magnitude, respectively. Benefiting from the unique structure, the composite at 5 wt % shows a 40% improvement in thermal conductivity relative to pure rubber. This latex-based method provides a facile and effective strategy to design and fabricate advanced functional BNNS-based polymeric nanocomposites with a segregated filler network morphology and considerable property enhancements in direct competition with graphene sheets. The composites could be potentially used in heat dissipative tires or conveyor belts.

Access to Enantiomerically Pure P-Stereogenic Primary Aminophosphine Sulfides under Reductive Conditions.

Stereochemically pure phosphines with phosphorus-heteroatom bonds and P-centered chirality are a promising class of functional building blocks for the design of chiral ligands and organocatalysts. A route to enantiomerically pure primary aminophosphine sulfides was opened through stereospecific reductive C-N bond cleavage of phosphorus(V) precursors by lithium in liquid ammonia. The chemoselectivity of the reaction as a function of reaction time, substrate pattern, and chiral auxiliary was investigated. In the presence of exclusively aliphatic groups bound to the phosphorus atom, all competing reductive side reactions are totally prevented. The absolute configurations of all P-stereogenic compounds were determined by single-crystal X-ray diffraction analysis. Their use as synthetic building blocks was demonstrated. The lithium salt of (R)-BINOL-dithiophosphoric acid proved to be a useful stereochemical probe to determine the enantiomeric purity. Insights into the coordination mode of the lithium-based chiral complex formed in solution was provided by NMR spectroscopy and DFT calculations.

Birch Reduction of Asphaltenes. Synthesis of Hydroasphaltenes

Reduction of Ecuadorian asphaltenes by lithium in liquid ammonia (Birch conditions) yields asphaltene salts that can be protonated by tert-butyl alcohol to yield deflocculated hydroasphaltene. Stud...

ChemInform Abstract: Reduction of Manganese Dioxide by Dissolved Lithium in Liquid Ammonia for Li‐Mn‐O Spinels.

AbstractLi1.12Mn1.88O4 spinel is synthesized by reduction of MnO2 by lithium dissolved in liquid ammonia (‐33 °C) and subsequent heat treatment (600—700 °C, 5—10 h).

Reduction of Manganese Dioxide by Dissolved Lithium in Liquid Ammonia for Li–Mn‐O Spinels

AbstractSpinel‐structured Li‐Mn−O compounds are considered as alternative cathode materials for high‐power lithium ion batteries, which are the ideal power source for the electric vehicles in the near future. However, synthesizing Li‐Mn−O spinels with good cycle performance is a difficult task. In this work, the lithium‐ammonia solution is used to perform the reduction of manganese dioxide (MnO2), which demonstrates a new reaction process for preparing Li‐Mn−O spinels. The whole processes for the formation of Li‐Mn−O spinels are proposed and the Li1.12Mn1.88O4 spinel, as an example, is easily achieved via a simple annealing process. Galvanostatic charge/discharge results indicate that the resulting Li1.12Mn1.88O4 spinel exhibits both of high capacity (∼105 mAhg−1 at 1C) and good cycling stability (500 cycles), even at the elevated temperature (∼55 °C). The present reaction conditions are interesting, especially, for preparing Li‐contained compounds, which can be extended for other cathode materials.

A practical preparation of the key intermediate for penems and carbapenems synthesis

A novel, practical and stereoselective synthesis of (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone, a key intermediate in the preparation of β-lactam antibiotics is reported. The crucial step of the synthesis is based on the Cu(I)-mediated Kinugasa cycloaddition/rearrangement cascade between silyl protected (R)-3-butyn-2-ol and the nitrone derived from benzyl hydroxylamine and benzyl glyoxylate. The obtained adduct is subjected to debenzylation with sodium, or lithium in liquid ammonia followed by oxidation with lead tetraacetate to afford the final product.

Birch Reduction of Graphite. Edge and Interior Functionalization by Hydrogen

The Birch reduction (lithium in liquid ammonia) of graphite gives a highly reduced, exfoliated product that is free of lithium. Edge and interior hydrogenation were demonstrated by solid-state (13)C NMR spectroscopy. Elemental analysis of a carefully purified sample allows the chemical composition to be expressed as (C(1.3)H)(n). Atomic force microscopy images showed that the reduced graphene was highly exfoliated. Hydrogen mapping by electron energy loss spectroscopy showed that the entire surface of the reduced sample was covered by hydrogen, consistent with the NMR studies also indicating that hydrogen was added in interior positions of the graphene lattice as well as along the edge. A large band gap (4 eV) further establishes the high level of hydrogenation.

9α-hydroxylation of 25-fluoroponasterone a diacetonide in lithium-ammonia solution

25-Fluoroponasterone A diacetonide reacted with lithium in liquid ammonia to give 25-fluoro-9α,20-dihydroxyecdysone diacetonide whose hydrolysis afforded 25-fluoro-9α,20-dihydroxyecdysone 20,22-acetonide. Nonfluorinated analog of the latter was isolated previously from Silene italica ssp. nemoralis.

Stereospecific formation of 7,8β-dihydroanalogs at the reduction of ponasterone acetonide with lithium in liquid ammonia

The reduction of ponasterone A diacetonide with lithium in liquid ammonia stereospecifically led to 7,8β-dihydroanalogs of 5α- and 5β-epimers of ponasterone A and 7,8β-dihydro-6α-hydroxy derivative. 7,8β-Dihydroponasterone A, phytoecdysteroid from the needles of Japanise yew Taxus cuspidata, and its 5α-epimer were synthesized.

Functionalization by Reductive Alkylation and Mapping of a Subbituminous Coal by Energy Dispersive X-ray Spectroscopy

Reduction of a subbituminous coal by lithium in liquid ammonia yields a coal salt that can be reacted with 1-iodododecane to yield dodecylated coal that is partially soluble in organic solvents. The coal salt also acts as an initiator for the in situ oligomerization of alkenes onto the surface of the coal nanoplatelets. Atomic force microscopy and high-resolution transmission electron microscopy images of this material have been recorded. Energy-dispersive X-ray spectroscopy has been used to identify minerals that occur in the coal.

Cyclopentanones Stereochemistry of the Lithium-Liquid Ammonia Reduction of 2, 3-Dialkyl-5-Hydroxy-2-Cyclopentenones

The stereochemistry of the lithium-liquid ammonia reduction of 2, 3-dimethyl-5-hydroxy-2-cyclopentenone (1) and 3-t.butyl-2-methyl-5-hydroxy-2-cyclopentenone (2) is studied in function of a set of proton donors. A high degree of stereoselectivity is observed as practically only two (predominantly one isomer) out of the eight diastereoisomeric 3, 4-dialkyl-1, 2-cyclopentane diols 3 or 4 are formed.

The Efficient and Enantiospecific Total Synthesis of Cyclopenta[b]phenanthrenes Structurally‐Related to Neurosteroids

We report an efficient synthesis of cyclopenta[b]phenanthrenes functionalized at C-3 and C-8 from an optically pure Hajos-Parrish ketone. The key step is a neutral alumina catalyzed Michael addition of a Hajos-Parrish ketone derivative (4) to 1,7-octadien-3-one (2) in 98% yield. This Michael addition product went through Krapcho decarbomethoxylation, aldol condensation, lithium liquid ammonia reduction, Wacker oxidation and acid catalyzed cyclization to form cyclopenta[b]phenanthrene (1a) in 37% overall yield for the 7 steps.

Enantiospecific synthesis of ABC-ring system of A-nor and abeo 4(3→2) tetra and pentacyclic triterpenes

Enantiospecific synthesis of ABC-ring systems of A-nor and abeo 4(3→2) tetra and pentacyclic triterpenes has been accomplished starting from the readily available monoterpene ( R)-carvone. ( R)-Carvone was used as the B-ring of the target molecules. A lithium-liquid ammonia mediated cyclisation of δ,ɛ-unsaturated ester was employed for the cyclopentannulation at the C-5 and C-6 carbons of carvone and an RCM reaction was employed for the cyclohexannulation to generate the ABC-ring system of A-nor tetra and pentacyclic triterpenes. The strategy has been extended for the synthesis of the ABC-ring system of abeo 4(3→2) tetra and pentacyclic triterpenes.

Exfoliated soluble graphite

Reduction of graphite by lithium in liquid ammonia yields graphite salts that can be reacted with dodecyl iodide to yield soluble dodecylated graphite. The height of the soluble graphite nanoplatelets was determined by scanning tunneling microscopy (STM) to be 3.5 nm, corresponding to approximately 10 layers of graphene. Solubility in organic solvents was determined to be 20 mg/L in chloroform and 70 mg/L in 1,2,4-trichlorobenzene.

Soluble activated charcoal

Reduction of activated charcoal by lithium in liquid ammonia yields charcoal salts that can be reacted with dodecyl iodide to yield soluble dodecylated activated charcoal. Atomic force microscopy images reveal a heterogeneous size distribution of nearly spherical nanoparticles. High-resolution transmission electron microscopy images show a layered microcrystalline arrangement that becomes separated to form mostly single layered disordered structures after dodecylation. A 1H– 13C cross polarization magic angle spinning spectrum of the charcoal revealed a broad, featureless signal from sp 2 carbons and a much weaker broad signal from aliphatic carbons.

Attachment of Nitrogen and Oxygen Centered Radicals to Single-Walled Carbon Nanotube Salts

Carbon nanotube salts, prepared by treating single-walled carbon nanotubes (SWNTs) with lithium in liquid ammonia, react with N-halosuccinimide by electron transfer to generate transient radical anions that yield succinimidyl radicals and halide anions. Similarly, alkyl peroxides, when treated with SWNT salts, give rise to alkoxy radicals and alkoxides. The free radicals add to the sidewalls of nanotube salts to form succinimidyl and alkoxy derivatized SWNTs. The functionalized SWNTs can then be converted to amino and hydroxyl SWNTs by hydrolysis with hydrazine or with fuming sulfuric acid, respectively. Hydrolysis of alkoxy derivatized SWNTs with D2O/D2SO4 led to the deuterated analogue of hydroxy SWNT, as shown by Fourier transform infrared (FTIR) spectroscopy. These reactions constitute a two-step synthesis of aminated and hydroxylated SWNTs. Covalent sidewall functionalization was confirmed by thermal gravimetric analysis (TGA), Raman spectroscopy, FTIR spectroscopy, and high-resolution transmission e...

Unexpected formation of an oxetane cycle by oxidation of diacetonide of 20-hydroxyecdysone with oxygen in an alkaline medium

The diacetonides of 9α,14α-epoxy-14-deoxy-20-hydroxyecdysone and 14α-hydroperoxy-14-deoxy-20-hydroxyecdysone have been obtained by the interaction of diacetonide of 20-hydroxyecdysone with a solution of lithium in liquid ammonia and following treatment with ammonia chloride and atmospheric oxygen.

Novel ecdysteroid analogs with oxygen-containing heterocycles in the steroid skeleton

The reaction of ecdysteroids (20-hydroxyecdysone and its acetonides) with lithium in liquid ammonia gave novel analogs with an oxetane 9α,14α-oxacycle in the steroid skeleton. In aqueous alcohol solution the 9,14-oxa analogs rearrange to the more stable 9α,13α-oxa analogs through a 1,2-migration of the 18-Me group from the C-13 to the C-14 atom.

SET Mechanism in the Functionalization of Single-Walled Carbon Nanotubes

Dispersions of carbon nanotube salts prepared by treating single-walled carbon nanotubes (SWNTs) with lithium in liquid ammonia react with aryl and alkyl sulfides by single electron transfer (SET) to yield transient radical anions that dissociate into carbon-centered free radicals and mercaptide. The free radicals add to the sidewalls of the nanotubes or recombine with SWNT radical anions. AFM images indicate that the derivatized SWNTs are partially debundled. Disulfides react with carbon nanotube salts to yield SWNTs functionalized by sulfur-centered radicals.

Observations on the Reductive Ring Opening Reactions of Alkylidenecyclopropyl Ketones Promoted by Lithium in Liquid Ammonia.

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