First regioselective enzymatic alkoxycarbonylation of primary amines. Synthesis of novel 5'- and 3'-carbamates of pyrimidine 3',5'-diaminonucleoside derivatives including BVDU analogues

The first regioselective enzymatic alkoxycarbonylation of primary amino groups has been achieved in pyrimidine 3',5'-diaminonucleoside derivatives. Thus, Candida antarctica lipase B (CAL-B) catalyzed this reaction with nonactivated homocarbonates allowing the selective synthesis of several N-5' carbamates, including (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) analogues, with moderate-high yields, whereas immobilized Pseudomonas cepacia lipase (PSL-C) afforded mixtures of alkoxycarbonylated regioisomers. To obtain N-3' carbamates selectively, a short and efficient chemoenzymatic route was used employing some of the N-5'-protected derivatives previously synthesized.     

Role of water in the chemisorption of PCl3 and POCl3 on pyrogenic silica

The interaction of gaseous PCl₃ and POCl₃ with dried and wetted pyrogenic silica has been studied by IR spectroscopy. The acceleration of the chemisorption accompanied by the formation of Si−O−P bonds in the presence of water vapor has been observed only with phosphorus trichloride.     

One-pot and regioselective synthesis of polysubstituted 3,4-dihydroquinazolines and 4,5-dihydro-3H-1,4-benzodiazepin-3-ones by sequential Ugi/Staudinger/aza-Wittig reaction

An efficient one-pot and regioselective synthesis of 3,4-dihydroquinazolines and 4,5-dihydro-3H-1,4-benzodiazepin-3-ones by Ugi/Staudinger/aza-Wittig sequence has been developed. The Ugi reactions of 2-azidobenzylamines, aldehydes, acids (or α-keto acids) and isocyanides produced the azide intermediates, which were then treated with tributylphosphine or triphenylphosphine to give polysubstituted 3,4-dihydroquinazolines or 4,5-dihydro-3H-1,4-benzodiazepin-3-ones in moderate to good yields by tandem Standinger/aza-Wittig reactions.     

35Cl Nqr spectroscopy of the [PO2Cl2]− and POCl3 groups in Me(PO2Cl2)2·2D (Me = Mg,Ca, Mn; D = POCl3,CH3COOC2H5,CH3COCH3)

³⁵Cl NQR spectra of dichlorophosphates Me(PO₂Cl₂)₂ · 2D (Me = Mg, Ca, Mn; D = CH₃COOC₂H₅, CH₃COCH₃, POCl₃) are studied in the temperature range 77 ? T (K) ? 305. It is shown that the three compounds with CH₃COOC₂H₅ as donor are isomorphic at 77 K, the crystal structure of Mn(PO₂Cl₂)₂· 2CH₃COOC₂H₅. The structure of Mg(PO₂Cl₂)_2^?· 2CH₃COCH₃ and of Mg(PO₂Cl₂)₂ · 2POCl₃ probably consists of infinite chains as found for Mn(PO₂Cl₂)₂· 2CH₃COOC₂H₅. Mg(PO₂Cl₂)₂· 2CH₃COOC₂H₅ shows phase transformations and a complicated dynamical behaviour leading to strong deviations from a Bayertype NQR function v = f(T). The donor capacity of POCl₃ in Mg(PO₂Cl₂)₂· 2POCl₃ is comparable with the donor strength in AsCl₃ · POCl₃ · A d_π-p_π overlap of the P-O bond influences the P-Cl bond.     

Synthesis of the First Thorium-Containing Nitride Perovskite, TaThN3

TaThN₃ can be prepared from a reaction of Ta₂Th₂O₉ and Ca₃N₂ at 1100-1500°C or from a reaction of Ta₃N₅ and Th₃N₄ at 1400°C. This black polycrystalline material crystallizes in the perovskite structure type with a = 4.020(6) Å.     

Synthesis, crystal structures and photoluminescence properties of new oxyborates, Mg5NbO3(BO3)3 and Mg5TaO3(BO3)3, with novel warwickite-type superstructures

Single crystals of new oxyborates, Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃, were prepared at 1370 °C in air using B₂O₃ as a flux. They were colorless and transparent with block shapes. X-ray diffraction analysis of the single crystals revealed Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ to be isostructural. The X-ray diffraction reflections were indexed to the orthorhombic Pnma (No. 62) system with a=9.3682(3) Å, b=9.4344(2) Å, c=9.3379(3) Å and Z=4 for Mg₅NbO₃(BO₃)₃ and a=9.3702(3) Å, b=9.4415(3) Å, c=9.3301(2) Å and Z=4 for Mg₅TaO₃(BO₃)₃. The crystal structures of Mg₅NbO₃(BO₃)₃ and Mg₅TaO₃(BO₃)₃ are novel warwickite-type superstructures having ordered arrangements of Mg and Nb/Ta atoms. Polycrystals of Mg₅NbO₃(BO₃)₃ prepared by solid state reaction at 1200 °C in air showed broad blue-to-green emission with a peak wavelength of 470 nm under 270 nm ultraviolet excitation at room temperature.     

Synthesis of novel analogues of antimycin A3

Four novel analogues of antimycin A₃, 1a-d, were synthesized in good overall yields.     

An efficient method for chlorination of alcohols using PPh3/Cl3CCONH2

A new and convenient method for the chlorination of alcohols utilizing PPh₃/Cl₃CCONH₂ is addressed. Various alcohols could smoothly be converted into their corresponding alkyl chlorides in high yield under mild conditions with short reaction times. A mechanism is disclosed with the evidence of inversion of configuration of the analogous alkyl chloride derived from R-(−)-2-octanol.     

Synthesis, crystal structure, spectrum properties, and electronic structure of a novel non-centrosymmetric borate, BiCd3(AlO)3(BO3)4

A novel non-centrosymmetric borate, BiCd₃(AlO)₃(BO₃)₄, has been prepared by solid state reaction methods below 750 °C. Single-crystal XRD analysis showed that it crystallizes in the hexagonal group P6₃ with a=10.3919(15) Å, c=5.7215(11) Å, Z=2. In its structure, AlO₆ octahedra share edges to form 1D chains that are bridged by BO₃ groups through sharing O atoms to form the 3D framework. The 3D framework affords two kinds of channels that are occupied by Bi³⁺/Cd²⁺ atoms only or by Bi³⁺/Cd²⁺ atoms together with BO₃ groups. The IR spectrum further confirmed the presence of BO₃ groups. Second-harmonic-generation measurements displayed a response of about 0.5×KDP (KH₂PO₄). UV-vis diffuse reflectance spectrum showed a band gap of about 3.19 eV. Solid-state fluorescence spectrum exhibited the maximum emission peak at around 390.6 nm. Band structure calculations indicated that it is an indirect semiconductor.     

RbAuUSe3, CsAuUSe3, RbAuUTe3, and CsAuUTe3: Syntheses and structure; magnetic properties of RbAuUSe3

The compounds RbAuUSe₃, CsAuUSe₃, and RbAuUTe₃ were synthesized at 1073 K from the reactions of U, Au, Q, and A₂Q₃ (A=Rb or Cs; Q=Se or Te). The compound CsAuUTe₃ was synthesized at 1173 K from the reaction of U, Au, Te, and CsCl as a flux. These isostructural compounds crystallize in the KCuZrS₃ structure type in space group Cmcm of the orthorhombic system. The structure consists of layers that contain nearly regular UQ₆ octahedra and distorted AuQ₄ tetrahedra. The infinite layers are separated by bicapped trigonal prismatic A cations. The magnetic behavior of RbAuUSe₃ deviates significantly from Curie–Weiss behavior at low temperatures. For T>200 K, the values of the Curie constant C and the Weiss constant θ_p are 1.82(9) emu K mol⁻¹ and −3.5(2)×10² K, respectively. The effective magnetic moment μ_eff is 3.81(9) μ_B. Formal oxidation states of A/Au/U/Q may be assigned as +1/+1/+4/−2, respectively.     

A Convenient Synthesis of 3- and 3,4-Substituted 4,5-Dihydroisoxazole-5-Acetic Acids

The 4,5-dihydroisoxazole-5-acetic acids 4a-j were prepared from the ketoximes 1a-j, 2,2-dimethyl-5-methoxymethylene-1,3-dioxan-4,6-dione (2) and butyllithium in yields from 35 to 79%.     

Synthesis of novel salts with HF, AsF3 and XeF2 as ligands to metal cations

A review of all known compounds of the type [Mⁿ(L)_m](AF₆)_n (M is a metal in the oxidation state n; A = P, As, Sb and Bi; L = HF, AsF₃ and XeF₂) is given with the emphasis on the compounds isolated and characterized by our group. The synthetic routes for the preparation of these compounds are given together with a brief analysis of their structures. In the case of L = XeF₂ the influence of the properties of the cation and the anion on the structural diversity of these coordination compounds is discussed. A brief analysis of their Raman spectra is also given.     

Synthesis and crystal chemistry of NH3(MoO3)3

NH₃(MoO₃)₃ crystallizes with hexagonal symmetry, space group $\text{P6}{}_3\text{m}$, lattice constants a = 10.568 Å, c = 3.726 Å, and Z = 2. The crystal structure has been determined by Patterson synthesis and refined assuming isotropic temperature factors to a final conventional R value of 0.085. The structure shows a three-dimensional arrangement built up of double chains of distorted MoO₆ octahedra, parallel to the [001] direction. The octahedral double chains are linked among each other through common oxygen atoms. In addition to the shared oxygen atoms, each molybdenum is coordinated to one terminal oxygen. MoO distances range from 1.645 to 2.378 Å and OMoO angles from 74.3 to 114.3°. These results are consistent with the fact that molybdenum in high-valence states shows octahedral coordination with terminal oxygens.     

Synthesis and characterization of novel magnetic Fe3O4/polyphosphazene nanofibers

Novel magnetic Fe₃O₄/polyphosphazene nanofibers were successfully prepared via a facile approach by ultrasonic irradiation. The structure and morphology were characterized by SEM, TEM, EDX, IR and XRD. The characterization results show that the magnetic Fe₃O₄/polyphosphazene nanofibers are several microns in length and 50–100 nm in diameter with Fe₃O₄ nanoparticles of 5–10 nm attached on the surface. The interaction between Fe₃O₄ nanoparticles and polyphosphazene nanofibers was thought as coordination behavior. TG curves show that the magnetic Fe₃O₄/polyphosphazene nanofibers have good thermostability and high magnetism content of about 44%. Magnetic studies show that the magnetic nanofibers exhibit good superparamagnetic properties with high magnetization saturation value of about 36 emu/g.     

Thermal decomposition of organo-bielemental vanadium compounds Cp2V(ER3) (ER3 - GeEt3, SnEt3, CH2SiMe3 SeGeEt3)

The thermal decompositon of a number of organo-bielemental vanadium compounds with the general formula Cp₂V(ER₃) (ER₃ - GeEt₃, SnEt₃, CH₂SiMe₃, SeGeEt₃) has been investigated in solids and in solution. The main decomposition products of Cp₂V(SnEt₃) are vanadocene and hexaethyldistannane. Et₃GeH, Et₃GeCp, Cp₂V and CpV(C₅H₄GeEt₃) are formed from Cp₂V (GeET₃) decomposition. Isolated CpV(C₅H₄GeEt₃) is characterized by IR and mass spectra. The decomposition of Cp₂V(CH₂SiMe₃) is accompanied by Me₄Si, Cp₂V and CpV-(C₅H₄CH₂SiMe₃) formation, the latter is identified from the mass spectrum. Triethylgermane, vanadocene, and a diselenide of vanadium are isolated on decomposition of Cp₂V(SeGeEt₃). Based upon the experimental data, mechanisms for the decompositon are proposed.     

Microwave-assisted one-pot regioselective synthesis of 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines

A protocol for regioselective one-pot synthesis of 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines under controlled microwave heating has been developed. Starting from commercially available 2-aminophenols, a base-mediated regioselective O-alkylation took place with 2-bromoalkanoates to give the acyclic intermediates, which underwent spontaneously an intramolecular amidation reaction to furnish 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines in 44-82% yields. For the acyclic intermediate possessing an electron-withdrawing group, microwave heating was necessary for the annulation reaction.     

New thallium iodates—Synthesis, characterization, and calculations of Tl(IO3)3 and Tl4(IO3)6, [Tl3Tl(IO3)6]

Two new thallium iodates have been synthesized, Tl(IO₃)₃ and Tl₄(IO₃)₆ [Tl⁺₃Tl³⁺(IO₃)₆], and characterized by single-crystal X-ray diffraction. Both materials were synthesized as phase-pure compounds through hydrothermal techniques using Tl₂CO₃ and HIO₃ as reagents. The materials crystallize in space groups R-3 (Tl(IO₃)₃) and P-1 (Tl₄(IO₃)₆). Although lone-pairs are observed for both I⁵⁺ and Tl⁺, electronic structure calculations indicate the lone-pair on I⁵⁺ is stereo-active, whereas the lone-pair on Tl⁺ is inert.     

Complex salts (DienH3)[IrCl6](NO3), (DienH3)[PtCl6](NO3), and (DienH3)[IrCl6]0.5[PtCl6]0.5(NO3): Synthesis, structure, and thermal properties

The complex salts ((DienH₃)[IrCl₆](NO₃) (I), (DienH₃)[PtCl₆](NO₃) (II), and (DienH₃)[IrCl₆]_0.5[PtCl₆]_0.5(NO₃) (III) (where Dien is NH₂(CH₂)₂NH(CH₂)₂NH₂) were synthesized and characterized by elemental, X-ray diffraction, and thermal analyses and by electronic and IR spectroscopies. Solid solution of the composition Ir_0.35Pt_0.65 was obtained by decomposition of compound III in the atmosphere of hydrogen. Original Russian Text ? E.V. Makotchenko, I.A. Baidina, P.E. Plusnin, L.A. Sheludyakova, Yu.V. Shubin, S.V. Korenev, 2007, published in Koordinatsionnaya Khimiya, 2007, Vol. 33, No. 1, pp. 47–54.