Chemoselective reduction of aldehydes and ketones by potassium diisobutyl-t-butoxy aluminum hydride (PDBBA)

t-Butoxy derivatives of DIBALH [lithium diisobutyl-t-butoxyaluminum hydride (LDBBA), sodium diisobutyl-t-butoxyaluminum hydride (SDBBA), and potassium diisobutyl-t-butoxyaluminum hydride (PDBBA)] were examined as chemoselective reducing agents of carbonyl compounds. Among them, PDBBA was found to be the most efficient for the reduction of aldehydes and ketones to the corresponding alcohols in the presence of ester, amide, and nitrile substituents at ambient temperature. In addition, the optimal conditions gave higher chemoselectivity for aldehydes in the presence of ketones.     

Synthesis and crystal structures of organometallic compounds containing the ligands C(SiMe3)2(SiMe2H) and C(SiMe2Ph)2(SiMe2H)

Metallation of (HMe₂Si)(Me₃Si)₂CH (1) by LiMe gave the organolithium compound Li(THF)₂C(SiMe₃)₂(SiMe₂H) (2a), which exists in toluene solution as a mixture of covalent species and ion pairs [Li(THF)₄][Li{C(SiMe₃)₂(SiMe₂H)}₂] (2b). Treatment of a mixture of 1 and LiMe with KOBu^t gave KC(SiMe₃)₂(SiMe₂H) (3). This reacted with AlMe₂Cl in hexane/THF to give Al(THF)Me₂{C(SiMe₃)₂(Si Me₂H)} (4). Treatment of (HMe₂Si)(PhMe₂Si)₂CH (5) with LiMe in Et₂O/THF gave the THF adduct [Li(THF)₂C(SiMe₂Ph)₂(SiMe₂H)] (6); in the presence of KOBu^t the solvent-free [K][C(SiMe₂Ph)₂(SiMe₂H)] (7) was obtained. Crystal structure determinations showed that 6 crystallizes in a molecular lattice and 7 in an ionic lattice in which the coordination sphere of the potassium comprises phenyl groups and hydrogen atoms attached to silicon, as well as the central carbon of the bulky carbanion. Compound 7 reacted with an excess of AlMe₂Cl to give [AlClMe{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (8) and AlMe₃. A small amount of the methoxo derivative [Al(OMe)Me{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (9) was obtained as a byproduct, presumably after the accidental admission of traces of air. X-ray structural determinations showed that 8 forms halogen-bridged dimers, with the bulky ligands in the anti-configuration, and 9 forms methoxo-bridged species in which the bulky ligands are syn.     

Vibrational study of hydrogen bonding and structural disorder in Na2H(SO4)2, K3H(SO4)2 and (NH4)3H(SO4)2 crystals

Infrared and Raman spectra on Na₃H(SO₄)₂, K₃ H(SO₄)₂ and (NH₄)₃ H(SO₄)₂ crystals have been investigated at 300 and 100 K in the 4000 to 30 cm⁻¹ region. An assignment of bands in terms of OH group frequencies and more or less distorted tetrahedra of ammonium and sulphate ions is given. The crystallographic and spectroscopic symmetry and/or dissymetry of OHO hydrogen bonds linking sulphate ions into dimers is discussed using OH group frequencies and the splitting of the v₁ (SO₄) Raman bands as criteria. In the particular case of (NH₄)₃H(SO₄)₁ compound containing several solid phases it can be shown that the room temperature phase (II) is strongly disordered, principally because of an orientational disorder of ammonium ions, and that a progressive ordering takes place with temperature lowering.     

A catalytic Koenigs-Knorr glycosylation based on acceptor activation with In(NTf2)3

The development of efficient glycosylation methods is important for gaining better insight into biological processes of significance to medicinal chemistry. Herein, we describe an In(NTf₂)₃ -catalyzed Koenigs-Knorr glycosylation based on the activation of an alcoholic hydroxyl group. A catalytic amount of In(NTf₂)₃ enables effective glycosylation of diverse alcohols with peracylated aldosyl bromides as donors, leading to the stereoselective formation of a series of glycosides in satisfactory yields. The protocol is characterized by mild reaction conditions and good functional-group tolerance, while obviating any need for any additive. Moreover, the potential utility of this transformation is demonstrated by the convenient syntheses of key building blocks for biomolecules of medicinal relevance.     

Synthesis and structures of new metallocene derivatives of lanthanides. Molecular structures of the complexes (C13H9)2Eu(THF)2 and (C5Me4H)2YbI(THF)

The divalent europium bis-fluorenyl complex (C₁₃H₉)₂Eu(THF)₂ was synthesized by the metathesis reaction of EuI₂(THF)₂ with two equivalents of fluorenylpotassium and by the protolytic substitution of the naphthalene ligand in the (C₁₀H₈)Eu(THF)₂ complex using the reaction with fluorene. According to X-ray diffraction data, the complex displays a skewed sandwich structure, in which one fluorenyl ligand is η⁵-coordinated to the metal atom, whereas the η³-coordination mode makes a great contribution to the coordination of another ligand. The (C₅Me₄H)₂YbI(THF) complex was synthesized by the reaction of YbI₃(THF)₂ with two equivalents of (C₅Me₄H)K. The structure of the complex was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 530–534, March, 2008.     

Synthesis of quinolines from amino alcohol and ketones catalyzed by [IrCl(cod)]2 or IrCl3 under solvent-free conditions

2-Aminobenzyl alcohol reacted with 2 equiv amount of ketones under the influence of [IrCl(cod)]₂ or IrCl₃ and KOH without any solvent, giving the corresponding quinoline derivatives in good yields.     

An IR study of the Ziegler system Co(acad)3/Mg(n-butyl)2 in THF

Applying IR spectroscopy for studying the Ziegler system Co(acac)₃/Mg(Bu)₂ (Bu=n-butyl) in tetrahydrofuran, it could be shown that the following reactions take place: reduction of cobalt (III), exchange of the acetylacetonate groups and their interaction with Mg(Bu)₂.

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Co(acac)₃/Mg(Bu)₂ (Bu=-) - , (III), Mg(Bu)₂.

     

Attempts at stepwise reduction of the carbon-nitrogen triple bond of a nitrile at two metal centres: study of the reactivity of [(CO)(PPh3)2Re( (μ-NCHPh)Ru(PPh3) 2(PhCN)] towards tetrafluoroboric acid and dihydrogen

The reaction of [(CO)PPh₃)₂Re(μ-H)₂(μ-NCHPh)Ru(PPh₃)₂(PhCN)] (2) with HBF₄-Me₂O generates [(CO)PPh₃)₂Re(μ- H)₂(μ,η¹,η²HNCHPh)Ru(PPh₃)₂(PhCN)][BF₄] (3). Monitoring the reaction by NMR spectroscopy shows the intermediate formation of [(CO)(PPh₃)₂ HRe(μ-H)₂(μ-NCHPh)Ru(PPh₃)₂(PhCN)][BF₄] (4). Attempted reduction of the imine ligand by a nucleophile (H⁻ or CN⁻) failed, regenerating 2. Under dihydrogen at 50 atm, 3 is slowly transformed into [(CO)(PPh₃)₂HRe(μ-H)₃Ru(PPh₃)₂(PhCN)][BF₄] (5) with liberation of benzyl amine.     

Total synthesis of (±)-camphorataimides and (±)-himanimides by NaBH4/Ni(OAc)2 or Zn/AcOH stereoselective reduction

Maleic anhydride 1 of Antrodia camphorate, which can be isolated from Chinese herbal medicine, is achieved in which the longest linear sequence is only five steps, in 40% overall yield from commercially available succinic anhydride. The crucial antrodimides 3 and 2 can be readily transformed by the chemoselective reduction with Zn/AcOH and NaBH₄/Ni(OAc)₂·4H₂O to afford the naturally occurring camphorataimides, 4 and 5, in high yields as well, respectively. This synthetic strategy can also be modified to give access to a variety of different maleic acid derivatives, himanimides 6-8.     

Proton dynamics in superionic phase of Tl3H(SO4)2

Electrical properties and ¹H-NMR absorption line have been measured, in order to investigate proton dynamics in a superionic phase in Tl₃H(SO₄)₂. From the measurement of the thermoelectric power, it is found that a majority carrier in electrical conductivity is a proton. Moreover, from ¹H-NMR measurement it is also found that the activation energy 0.33 eV of the hopping motion of protons is close to 0.38 eV as observed in the electrical conductivity measurement. These results indicate that the electrical conductivity in the superionic phase is caused by the hopping motion of protons accompanied by the breaking of the hydrogen bonds.     

Raman spectroscopic study of K3H(SO4)2 (phases I and II) single crystals

A Raman study of K₃H(SO₄)₂ as a function of temperature reveals that this compound undergoes a phase transition at T_c = 483 K prior to the decomposition at 508 K.     

Preparation of dinitrogen complexes Mo(N2)2P4 stabilised by phosphonite PPh(OEt)2 and phosphinite PPh2(OEt) ligands

Dinitrogen complexes Mo(N₂)₂P₄1, 2 [P=PPh(OEt)₂ and PPh₂OEt] were prepared by allowing a MoCl₃(THF)₃ solution containing an excess of phosphine to react with magnesium under nitrogen. Substitution reactions with CO and p-tolylisocyanide were studied, and led to Mo(CO)₂P₄, Mo(CO)₃P₃, and Mo(p-tolylNC)₂P₄ derivatives. Treatment of dinitrogen compound Mo(N₂)₂[PPh(OEt)₂]₄ with an excess of HCl gave the hydrazido(2-) [MoCl(NNH₂){PPh(OEt)₂}₄]Cl derivative. Reduction reactions with zinc amalgam of complexes 1 and 2 in the presence of lutidine·HCl gave ammonia in about 8-10% yield.     

Co3{CH3C(NH3)(PO3H)(PO3)}2 {CH3C(NH3)(PO3H)2}2(H2O)4·2H2O: A cobalt 1-aminoethylidenediphosphonate with a layer structure

This paper describes the structure and magnetic properties of a novel cobalt 1-aminoethylidenediphosphonate compound, namely Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂{CH₃C(NH₃)(PO₃H)₂}₂(H₂O)₄·2H₂O (1). The structure contains a trimer unit of Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂ in which two equivalent phosphonate ligands chelate and bridge the three cobalt ions. Each trimer unit is further linked to its four equivalent neighbors through corner-sharing of CoO₆ octahedra and CPO₃ tetrahedra, forming a two-dimensional layer in the bc-plane which contains 12-membered rings. These layers are connected to each other by extensive hydrogen bonds. Magnetic studies show that weak antiferromagnetic interactions are mediated between the cobalt ions. Crystal data for 1: monoclinic, space group C2/c, a=27.727(4), b=7.1091(11), , β=118.488(3), , Z=2.     

Reactions of [LiC(SiMe2H)3]·2THF: Sterically hindered tris(dimethylsilyl)methane derivatives and their hydrosilylation

Treatment of LiC(SiMe₂H)₃]·2THF (1) with alkeny1chlorosilanes produced sterically hindered alkenylsilanes (4–10) of structure H₂C=CH---(CH₂)_nSiRR′C(SiMe₂H)₃ (R=Me; R′=Me or Cl; n=0, 1, or 4). The Peterson reaction of 1 with carbonyl compounds gave sterically hindered olefins R(R′)C=C(SiMe₂H)₂. Pt or Rh catalyzed intramolecular hydrosilylation of H₂C=CHSiMe₂C(SiMe₂H)₃ (4) occurred to produce a new 1,3-disilacyclobutane derivative 15. Intermolecular hydrosilylation was favored for 5, 8, and 10, producing oligomeric products.     

Formation of the lithium alkylaluminium secondary amide [Me2Al{(PhCH2)2N}2Li·THF] by a methane elimination/amide insertion process

Synthesised by refluxing the amine adduct [Me₃Al·(PhCH₂)₂NLi·HN(CH₂Ph)₂] in toluene/THF, the title compound has been structurally characterised by X-ray diffraction, and the methane elimination/amide insertion processes involved in its formation have been modelled theoretically through a series of ab initio MO calculations.     

Nano-Li3V2(PO4)3/C Synthesized by Thermal Polymerization Method as Cathode Material for Lithium Ion Batteries

A nano-Li₃V₂(PO₄)₃/C powder was successfully prepared by a thermal polymerization method. The particle sizes of the intermediate product powder and the final product Li₃V₂(PO₄)₃ are all less than 200 nm. The carbon is partially coated on the surface of Li₃V₂(PO₄)₃ particles and the rest exists between particles with a total carbon content of 4.6wt%. This nano-Li₃V₂(PO₄)₃/C sample shows a discharge capacity of 124 mAh/g without capacity fading after 100 cycles at 0.1 C in the voltage rang of 3.0-4.3 V. Excellent rate performance is also achieved with a capacity of 80 mAh/g at 20 C in 3.0-4.3 V and 100 mAh/g at 10 C in 3.0-4.8 V. This study suggests that the thermal polymerization method is suitable to synthesize nano-Li₃V₂(PO₄)₃/C materials.     

Diastereoselective synthesis of cyclic 1,3-aminoalcohols bearing CF3(CCl3)-groups

An aldol-type reaction of cyclic imines and cyclic lactims with carbonyl compounds activated by electron withdrawing trifluoromethyl or trichloromethyl groups proceeded without any catalyst under mild condition. β-Hydroxymethyl substituted cyclic imines or imidates are formed as a result of the reaction. The reduction of the prepared imines leads stereoselectively to the cyclic 1,3-aminoalcohols. Application of methyl trifluoropyruvate in this transformation opens an opportunity for the synthesis of γ-aminoacids derivatives which contain pyrrolidine moiety.