The chemistry and the stereochemistry of poly(N-alkyliminoalanes) : VI. A novel synthesis of poly(N-alkyliminoalanes) by reaction of alkali metal alanates with primary amines

A novel synthesis of poly(N-alkyliminoalanes) (PIA) is reported. This involves the reaction in hydrocarbon solvents of LiAlH₄ or NaAlH₄ with primary amines having a nitrogen with α- or β- secondary carbon atoms or with tertbutylamine. Complexes of iminoalanes with alkali metal hydrides are obtained from linear amines. The same reaction carried out in polar solvents always gives complexes of PIA with LiH or NaH and the solvent. This new synthesis is simpler and convenient for producing soluble and well characterized PIA, some of which are not obtainable by other methods.     

Investigations on the solid state interaction between LiAlH4 and NaNH2

In this paper, two LiAlH₄-NaNH₂ samples with LiAlH₄ to NaNH₂ molar ratio of 1/2 and 2/1 were investigated, respectively. It was observed that both samples evolved 2 equiv H₂ in the ball milling process, however, the reaction pathways were different. For the LiAlH₄-NaNH₂ (1/2) sample, Li₃Na(NH₂)₄ and NaAlH₄ were formed through cation exchange between reactants. The NaAlH₄ formed further reacts with Li₃Na(NH₂)₄ and NaNH₂ to give H₂, NaH and LiAlN₂H₂. For the LiAlH₄-NaNH₂ (2/1) sample, Li₃Na(NH₂)₄, LiNH₂ and NaAlH₄ were formed firstly through the same cation exchange process. The resulting LiNH₂ reacts with the remaining LiAlH₄ and produces H₂ and Li₂AlNH₂.     

First Synthesis of Dopamine and Rotigotin Analogue 2-Amino-6,8-dimethoxy-1,2,3,4-tetrahydronaphthalene

The title compound was synthesized starting from 3-(3,5-dimethoxyphenyl)acrylic acid in 11 steps with 30% total yield. The reaction sequence hydrogenation of acrylic acid, reduction of acid to alcohol derivative with LiAlH₄, reaction of alcohol with CBr₄/PPh₃, substitution reaction of alkyl halide to nitrile derivative with NaCN, hydrolysis of nitrile with NaOH, cyclization reaction of acid with PPA to give 1-tetralone, α-carboxylation of tetralone with Me₂CO₃ in the presence of NaH, reduction of ketone group with Et₃SiH, hydrolysis of ester, Curtius rearrangement of acid with diphenylphosphoryl azide followed by conversion to carbamate, and finally hydrogenolysis of carbamate afforded 2-amino-6,8-dimethoxy-1,2,3,4-tetrahydronaphthalene hydrogen chloride salt.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Synthesis and properties of potassium salts of per-<Emphasis Type="Italic">O</Emphasis>-carboxymethyl-calix[4]pyrogallols and their complexes with Cu<Superscript>2+</Superscript>, Fe<Superscript>3+</Superscript>, and La<Superscript>3+</Superscript>

Synthesis of water-soluble potassium salts of carboxymethyl derivatives of calix[4]pyrogallols and dodeca(carboxylatomethyl)tetramethylcalix[4]pyrogallol (L) complexes with transition metal ions (Cu²⁺, Fe³⁺, La³⁺) is described. Their structures in the solid state and in solution were characterized by NMR spectroscopy, ESR, and IR spectroscopy. Calix[4]pyrogallol dodecacarboxylates exist in the rccc-configuration. Calix[4]pyrogallol with methyl substituents at the lower rim in a wide range concentrations exists in water predominantly in the dimeric form. The obtained polynuclear transition metal complexes possess less symmetric structure than potassium salt of calix[4]pyrogallol (K₁₂L). All studied complexes contain water molecules bound by rather strong hydrogen bonds. At room temperature the Fe₄L complex is characterized by the environment of the Fe³⁺ ions close to octahedral. The absence of signals in the ESR spectrum of the Cu₆L complex indicates the strong antiferromagnetic interaction Cu²⁺-Cu²⁺.     

Hydrogen binding property of Co- and Ni-based organometallic compounds

The binding property of hydrogen on organometallic compounds consisting of Co, and Ni transition metal atoms bound to C _m H _m rings (m = 4, 5) is studied through density functional theory calculation. CoC _m H _m and NiC _m H _m complexes can store up to 3.49 wt% hydrogen with an average binding energy of about 1.3 eV. The adsorption characteristics of hydrogen to organometallic compounds are investigated by analyzing vibrational spectra of CoC₄H₄(H₂) _n and NiC₄H₄(H₂) _n (n = 0, 1, 2). The kinetic stability of these hydrogen-covered organometallic complexes is assured by analyzing the energy gap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals. It is also discussed the application of 18-electron rule in predicting maximum number of hydrogen molecules that could be adsorbed by these organometallic compounds.     

New synthesis of ( E )-3,7-dimethyl-2,7-octadienylpropionate and ( E )-3,7-dimethyl-2-octen-1,8-diol, pheromone components of San Jose scaleinsect Quadraspidiotus pernicious and african monarch butterfly Danaus chrysippus

6-Methyl-6-hepten-2-one (3) on reaction with ethyl α-dimethylphosphonate/NaH gives a mixture of (E)-and (Z)-conjugated esters. The major (E)-isomer, (E)-ethyl-3,7-dimethyl-2,7-octadienoate (4), on reduction with LiAlH₄ at room temperature furnishes (E)-3,7-dimethyl-2,7-octadien-l-ol (5) which on propionylation affords (E)-3,7-dimethyl-2,7-octadienyl propionate (1). Carbinol (5) is converted into its silyl ether (E)-2,6-dimethyl-8-t-butyldimethylsilyloxy-l,6-octadiene (6) witht-Bu(Me)₂SiCl in CH₂Cl₂, which on hydroboronation-oxidation with 9-BBN/NaOH-H₂O₂ followed by disilylalion with (n-Bu)₄N⁺ F⁻ at room temperature, gives (E)-3,7-dimethyl-2-octen-l,8-diol (2).     

A theoretical study of high-pressure-induced phases of LiAlH<Subscript>4</Subscript> using calculated NQCC parameters

Quadrupolar parameters of nuclei can be used as a tool to understand the electronic structure of compounds. Lithium alanate (LiAlH₄) is a potential hydrogen storage material because of its high capacity of 10.5 wt % H₂. However, the drawbacks of its dehydrogenation process are the relatively high temperatures and the slow dehydrogenation kinetics; furthermore, its reversibility is rather poor. Understanding the bonding nature of Al and H is essential for improving its dehydrogenation performance. In this work the charge density distribution in LiAlH₄ is studied. Thus using calculated nuclear quadrupole coupling constants of hydrogens (²H-NQCCs), the electronic structure of α-LiAlH₄ with high pressure forms of LiAlH₄, (β- and γ-LiAlH₄) were compared. The results show that easier condition for dehydrogenation is expected in β-LiAlH₄. Comparison of calculated dehydrogenation enthalpies of LiAlH₄ phases verifies this prediction. The electric field gradient (EFG) of quadrupolar nuclei were calculated to obtain NQCC parameters. All calculations performed using Gaussian 03 at B3LYP/6-31G* level of theory.     

Structure-dependent transformations of the tetrachlorocyclopentadienone dimer and the product of its substitutive rearrangement in reactions with NaBH4, CrCl2, LiAlH4, and Zn

Dechlorination of the tetrachlorocyclopentadienone dimer and perchloro-7-oxotricyclo[6.1.0.0^4,8]nona-2,5-diene-9-carboxylic acid N,N-diethylamide with hydride ion donors (NaBH₄, LiAlH₄, etc.) and electron donors (CrCl₂ or Zn) were studied. The possible pathways of unusual transformations of both sterically hindered molecules are considered. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1001–1007, June, 2006.     

In Situ Synthesis of 3D Flower‐Like Nanocrystalline Ni/C and its Effect on Hydrogen Storage Properties of LiAlH4

Lithium alanate (LiAlH₄) is of particular interest as one of the most promising candidates for solid‐state hydrogen storage. Unfortunately, high dehydrogenation temperatures and relatively slow kinetics limit its practical applications. Herein, 3D flower‐like nanocrystalline Ni/C, composed of highly dispersed Ni nanoparticles and interlaced carbon flakes, was synthesized in situ. The as‐synthesized nanocrystalline Ni/C significantly decreased the dehydrogenation temperature and dramatically improved the dehydrogenation kinetics of LiAlH₄. It was found that the LiAlH₄ sample with 10 wt % Ni/C (LiAlH₄‐10 wt %Ni/C) began hydrogen desorption at approximately 48 °C, which is very close to ambient temperature. Approximately 6.3 wt % H₂ was released from LiAlH₄‐10 wt %Ni/C within 60 min at 140 °C, whereas pristine LiAlH₄ only released 0.52 wt % H₂ under identical conditions. More importantly, the dehydrogenated products can partially rehydrogenate at 300 °C under 4 MPa H₂. The synergetic effect of the flower‐like carbon substrate and Ni active species contributes to the significantly reduced dehydrogenation temperatures and improved kinetics.     

Formation and properties of nickel catalysts for hydrogenation under the action of lithium Di- and tris(<Emphasis Type="Italic">tert</Emphasis>-butoxy)hydroaluminates

It was demonstrated that systems based on Ni(II) compounds and the alkoxyhydride derivatives LiAlH(tert-BuO)₃ and LiAlH₂(tert-BuO)₂, in contrast to LiAlH₄, exhibit high catalytic activity in the reaction of styrene hydrogenation in the absence of activators. The inhibiting effect of an excess of LiAlH₂(tert-BuO)₂ was found. The analysis of the composition of reaction mixtures by NMR, EPR, and UV spectroscopy and TEM showed that side reactions of the conversion of aluminum-containing components occurred together with the formation of nickel nanoclusters. The most probable reaction schemes of LiAlH(tert-BuO)₃ and LiAlH₂(tert-BuO)₂ disproportionation were proposed. The nature of the stabilizers of nickel nanoparticles was considered.     

Reduction of glycyrrhizic acid

The reduction of glycyrrhizic acid by NaBH₄ and LiAlH₄ was studied. The conditions for the selective reduction of the COOH groups of the carbohydrate chain and the C(11)=0 group of aglycon were found. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 875–877, April, 1997.     

Metalation of 1-R-2-benzyl-o-carboranes with lithium aluminum hydride

Carboranes with the general formula I-R-2-PhCH₂-1,2-C₂B₁₀H₁₀ (R = Me, Prⁱ, Ph, PhCH₂) are readily metalated with lithium aluminum hydride in a THF solution at the CH₂ group. In this case only one hydrogen atom in LiAlH₄ is substituted, and trihydride complexes 1-R-2-PhCH(AlH₃Li)-1,2-C₂B₁₀H₁₀, are formed, which are stable in a solutionTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1282–1284, May, 1996.     

NaH(ZnPO4)2及α-磷锌矿的低热固相反应合成与调控

对合成层状磷酸锌氢钠（NaH(ZnPO4)2）的新路线进行了研究,用Na2HPO4·12H2O及Zn(NO3)2·6H2O作为起始原料,聚乙二醇-400（PEG-400）为表面活性剂,通过一步固相反应于60 ℃下陈化得到了层状磷酸锌氢钠。用XRD, TG/DTG 及 FTIR表征了产物。实验结果表明,NaH(ZnPO4)2在500 ℃附近有一个主要的失重峰,归属为HPO42-脱水变成P2O74- 离子。因此,作为有机反应的非均相催化剂时,该化合物具有足够的热稳定性。对照实验的结果显示陈化温度调控着反应产物的生成。即,当反应混合物在60 ℃陈化时,生成的是NaH(ZnPO4)2,当反应混合物在室温陈化时,生成的则是α-Zn3(PO4)2·4H2O。     

α-(Benzotriazol-1-YL)Propargyl Ethyl Ethers: Novel Precursors to Enediynes,Enynes and Dienynes

Deprotonated 1-(benzotriazol-1-yl)propargyl ethyl ethers react with propargyl, allyl and alkyl bromides to give the expected substituted derivatives 2, 4 and 9, respectively. Subsequent eliminations of the benzotriazolyl group upon treatment with NaH or ZnBr₂, and elaboration of the acetylene group, generate ethoxy substituted enediynes 3, 6, 8, dienynes 7 and enynes 12. Grignard reagents or LiAlH₄ convert 9 into α-ethoxy substituted alkynes 10 and 11.     

Alkyl Ammonium Ion Selectivity of Hexahomotrioxacalix[3]arene Triamide Derivative having the Intramolecular Hydrogen-Bonding Group

The lower rim functionalized hexahomotrioxacalix[3]arene triamide 4 with cone-conformation was synthesized from triol 1 by a stepwise reaction. The different extractability for alkali metal ions, transition metal ions, and alkyl ammonium ions from water into dichloromethane is discussed. Due to the strong intramolecular hydrogen bonding between the neighboring NH and CO groups in triamide 4, its affinity to metal cations was weakened. Triamide 4 shows a single selectivity to n-BuNH₃⁺. The anion complexation of triamide 4 was also studied by ¹H NMR titration experiments. Triamide 4 binds halides through the intermolecular hydrogen bonding among the NH hydrogens of amide in a 1:1 fashion in CDCl₃. The association constants calculated from these changes in chemical shifts of the amide protons are K_a = 223 M⁻¹ for Cl⁻ and K_a = 71.7 M⁻¹ for Br⁻. Triamide 4 shows a preference for Cl⁻ complexation than Br⁻ complexation.     

Hydroxylammonium fluorometalate: synthesis and characterisation of a new fluorozincate

Abstract  

A new coordination compound of zinc fluoride and hydroxylammonium, (NH₃OH)₂ZnF₄, was obtained after dissolving zinc powder in hydrofluoric acid (40%) and adding solid hydroxylammonium fluoride. The colourless crystals were characterised chemically, magnetically, structurally by single-crystal X-ray diffraction analysis, and thermogravimetrically by TGA and DSC analysis. The structure consists of NH₃OH⁺ cations and ZnF₆ octahedra in which the metal ion lies on the inversion centre. Each of the ZnF₆ octahedra shares four of its vertices in a way that each vertex is shared between two octahedra. Oxygen and nitrogen atoms of hydroxylammonium cations are donors of hydrogen bonds. Hydroxylamonium fluorozincate crystallizes monoclinic, P21/c, with cell parameters a = 8.1604(4) ?, b = 5.8406(3) ?, c = 5.6586(2) ? and β = 94.745(3)°. The compound decomposes above 373 K in four steps, obtaining ZnO as the final residue. Magnetic properties of the compound were studied between 2 and 300 K, giving the prevailing diamagnetic behaviour with room temperature susceptibility of −9 × 10⁻⁵ emu mol⁻¹.     

Titanium-catalyzed hydrosilylation of olefins: A comparison study on Cp2TiCl2/Sm and Cp2TiCl2/LiAlH4 catalyst system

Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/Sm (Cp?=?cyclopentadienyl) under solvent free conditions have been investigated. By using Cp₂TiCl₂/Sm as catalyst system, β-adducts and hydrogenation products were detected. Hydrosilylation of olefins catalyzed by Cp₂TiCl₂/LiAlH₄ under room temperature has also been studied. The influence of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) on Cp₂TiCl₂/Sm and Cp₂TiCl₂/LiAlH₄, respectively, indicated that hydrosilylation of olefins catalyzed with Cp₂TiCl₂/Sm went through a free radical reaction pathway while a coordination mechanism was applied for Cp₂TiCl₂/LiAlH₄ catalyst system.     

Contracted CI calculations of models for catalytic reactions involving transition metals

Theoretical models for reductive elimination from transition metal containing molecules have been studied using large scale contracted CI calculations. Four different models were treated, namely, NiH₂, PdH₂, Ni(CH₃)₂, and Pd(H₂O)₂H₂, in order to study the effects of adding ligands, exchanging hydrogens with methyl groups, and comparing nickel and palladium. The most interesting result already appeared for the simplest system NiH₂. A closed-shell-type ¹A₁ state with a small bond angle of only 57° is bound compared to Ni and H₂ with only a very small barrier for formation. The bond distance is short, shorter than in NiH, and the d orbitals are strongly involved in the binding. The hydrogen atoms bind both to nickel and to each other. With methyl groups rather than hydrogens, this double sided bonding situation is destroyed and Ni(CH₃)₂ has a negative binding energy with the carbon bonds pointing towards nickel. For PdH₂ only a weakly bound complex between an essentially unchanged H₂ and Pd was found. The bond distance is very long. Adding H₂O ligands to Pd shortens the bond distance and significantly opens up the bond angle. The methods used in the investigation and the chemical implications of the results are discussed.     

Organometallic motifs in the structures of solid state ternary carbides of the late transition metals

Solid state ternary transition metal carbides containing carbon, a middle to late transition metal (Re to Ni), and a highly electropositive multivalent metal such as lanthanide, yttrium, or thorium exhibit a number of structural motifs resembling those in metal carbonyls and other transition metal derivatives of strong -acceptor ligands. This paper presents models for the chemical bonding in the transition metal—carbon subnetworks of the ternary late transition metal carbides LnCoC (Ln=lanthanide), Ln₂ReC₂, Th₂NiC₂, Ln₂FeC₄, Ln₃MC₄ (M=Fe, Co, Ni, Ru, Rh, Os, Ir), Ln₄NiC₅, Ca₄Ni₃C₅, and Er₈Rh₅C₁₂. Carbide ligands present in such materials include terminal C^4– in Th₂NiC₂ and Y₂ReC₂, ₂-C^4– in YCoC or Y₂ReC₂ similar to the central allene carbon atom, 1,2-bridging C ₂ ^4– in Sc₃CoC₄ formally derived from ethylene, ₃-bridging C ₂ ^4– in LnMC₂ (M=Fe, Co, Ni, Ru) formally derived from ethylene, and 1,1-bridging C ₂ ^2– in Ln₂FeC₄ isoelectronic with ₂-CO group in metal carbonyls.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1358–1366, August, 1994.     

A New Approach to Nicotine: Symmetry Consideration for Synthesis Design

A synthesis of nicotyrine ( 9 ), and hence formally racemic nicotine, was carried out by elaboration of the 1 : 1 adduct 2 of cycloocta‐1,5‐diene and chlorosulfonyl isocyanate (ClSO₂? NCO). Transformation of adduct 2 into carbamate 4 was followed by ozonolysis, tosylation, and NaH treatment, which led to pyrrolidinylpiperidinone 6 . LiAlH₄ Reduction, debenzylation, and aromatization yielded 2 .