Volume 61, Issue 3

The dilithium salt of di(tert-butyl-methyl)ketazine 1 reacts with the bimolar amount of ClSiMe 3 to give the di(tert-butyl-trimethylsilylmethylen)ketazine, 2. In the reaction of lithiated 2 and F 2 PN(iPr) 2 the 1,2-diaza-3-phosphacyclopent-5-ene (3) is formed. The dichlorophosphanes Cl 2 PC 6 H 5 and Cl 2 PCMe 3 react with 1 in boiling toluene to give the 1,2-diaza-3-phosphacyclopentenes 4 and 5. The oxygen of the air oxidizes 5 to the 1,2-diaza-3-phosphacyclopent-5-ene 6. Equivalent amounts of H 2 O cleave the ring skeleton of 5, the tert-butyl-methyl-(tert-butyl-(tert-butylphosphino)methylketazine 7 being formed. The 1,2-diaza-3-phosphacyclopenta-3,5-diene 8 and the 1,5-diaza-2,6-diphospha- bicyclo[3.3.0]octa-3,7-diene 9 are the reaction products of 1 and PCl 3 in toluene. 1 forms with HCl the hydrochloride 10. The 5-tert-butyl-1,2-diaza-3-phospha-cyclopenta-3,5-diene 11 is isolated from the reaction of 9 and MeLi. 11 is also obtained from PCl3 and tert-butyl-methyl-hydrazone in good yields. The cyclohexaphosphane 12 was formed in the reaction of 9 with Na/K alloy. The results of the crystal structure analyses of 2, 3, 6, 10, and 12 are reported.

Reaction of the /i-bis(tridentate) ligand H 3 L' (L' = 1,3-bis[N-(5-cliloro-2-hydroxybenzylidene)- 2-ainiiioetliylene]-2-(5-cliloro-2-hydroxy!phenyl)iniidazoliduie) with eopper(II) chlonde diliydrate gives the chair-piperazine bridged complex [Cu 2 (μ-L)Cl 2 ]. The halves of the binuclear complex are related by crystallographic inversion symmetry. The intramolecular Cu ・・・Cu separation is 6.954(3) Å. Temperature-dependent magnetic susceptibility measurements of the complex show a weak intramolecular antiferromagnetic eouphng. The super-exchange coupling constant (J) is - 10.5 cm -1 . Semi-empirical extended Huckel molecular orbital (EHMO) calculations have been performed in order to gain msight into the molecular orbitals that participate in the super-exchange pathway.

The reactions of n-hexyn-1-ylsilanes or arylethyn-1-ylsilanes, bearing methyl groups and one (2), two (3) or three hydride functions (4) at the silicon atom, with triallylborane 1 lead primarily to products of 1,1- or 1,2-allylboration. In the alkenes (5, 9, 13) formed by stereoselective 1,1-allylboration, with the silyl and the diallylboryl groups in cis-positions at the C=C bond an electron-deficient Si-H-B bridge is present. The activation of the Si-H bond in these alkenes induces intramolecular hydrosilylation under very mild reaction conditions to give 1,4-silabora-cyclohept-2-enes (7 and 11). The products of 1,2-allylboration (6, 10, 14) are further transformed into 1-boracyclohex-2-enes (8, 12, 15) and 7-borabicyclo[3.3.1]non-2-enes (16, 17) by intramolecular 1,2-allylboration reactions. The proposed structures are based on consistent sets of 1 H, 11 B, 13 C and 29 Si NMR data.

Pyrazolyl-substituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives have been synthesized by reaction of 1,4-benzoquinone and 1,4-naphthoquinone, respectively, with pyrazole. Cyclovoltammetric measurements have shown that 1,4-benzoquinone possesses the potential to oxidize 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene. The 2,5-bis(pyrazol-1-yl)- 1,4-dihydroxybenzene reacts with air to give quantitatively black insoluble 2,5-bis(pyrazol-1-yl)-1,4- quinhydrone. Black crystals of 2,5-bis(pyrazol-1-yl)-1,4-quinhydrone suitable for X-ray diffraction were grown from methanol at ambient temperature (monoclinic C2/c). The poor yields of pyrazolylsubstituted 1,4-dihydroxybenzene and 1,4-dihydroxynaphthene derivatives can be explained by the formation of insoluble black quinhydrons in the reaction of benzoquinone and naphthoquinone with pyrazole. The dianions of 2-(pyrazol-1-yl)- and 2,5-bis(pyrazol-1-yl)-1,4-dihydroxybenzene react with oxygen to give the corresponding semiquinone anions. 2,5-Bis(pyrazol-1-yl)-1,4-benzoquinone shows two reversible one-electron reduction processes in cyclovoltammetric measurements, whereas pyrazolyl-substituted 1,4-dihdroxybenzene and -naphthene derivatives undergo irreversibile electrontransfer processes.

While the diphosphadiboretane (tBuP=Btmp) 2 , 1, reacts with boron trihalides BX 3 (X = Cl, Br, I) with BN cleavage producing a number of unidentifiable products, a new tricyclic BP ring system 2, containing B 3 P 3 , PB 2 C 2 and C 6 rings, results from the combination of PhBCl 2 and 1. B-Chlorocatecholborane and 1 give access to the diborylphosphane 3, tmpBCl-PtBu-cat (cat = C 6 H 4 O 2 B). This shows that the selectivity of the reactions increases as the Lewis acidity of boron halide decreases. The structure of compounds 2 and 3 were determined by X-ray structure analysis. The bicyclic (tmpBP) 2 4 forms no adducts with MeI, CF 3 SO 2 Me or Ph 3 C(SnCl 5) . However, it adds B(C 6 F 5 ) 3 to give 10, the first BX 3 adduct of this bicycle that is fully characterized including its molecular structure.

Two new bis(5,5-diethylbarbiturato) (barb) complexes of zinc, [Zn(barb) 2 (en)] (1) and [Zn(barb) 2 (bpy)] ・H 2 O (2) [en = ethylenediamine, bpy = 2,2’-bipyridine], have been prepared and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in monoclinic space groups. The zinc(II) ions in complex 1 are tetrahedrally coordinated by two barb and an en ligand. The barb ligands are N-coordinated while the en ligand acts as a bidentate chelating ligand. One carbonyl oxygen atom of each barb ligands in complex 2 participates in the bonding with the zinc ion with remarkably long Zn-O bonds resulting in a highly distorted octahedral geometry. Molecules of complex 1 are connected via N-H ···O hydrogen bonds, involving hydrogen atoms of both barb and en ligands, while molecules of complex 2 are linked by N-H ···O and O-H ···O hydrogen bonds and also aromatic π(bpy) ···π(bpy) stacking interactions. The voltammetric behavior of complexes 1 and 2 was investigated in aqueous solution by cyclic voltammetry using a NH 3 /NH 4 Cl buffer. The cyclic voltammogram of 1 shows a cathodic peak at −1.260 V and an anodic peak at −1.068 V due to a quasi-reversible two-electron process. Complex 2 yields two reduction peaks at −1.312 and −1.412 V. The former corresponds to a quasi-reversible electrode process of the zinc(II) ions in complex 2, while the latter is attributed to the reduction of the coordinated bpy ligands.

A solid state synthesis of calcium manganite (CaMnO 3 ) is described where equimolecular mixtures CaCO 3 :MnCO 3 have been subjected to mechanical stress (high energy milling) so yielding CaCO 3 -MnCO 3 solid solutions of nanometric particle size. TG measurements have shown that a link exists between milling time, the extent of non-stoichiometry and the milling-induced decomposition of MnCO 3 to Mn 3 O 4 . A short (2 h) annealing at 850 °C performed on a sample mixture milled for 25 h leads to non-stoichiometric CaMnO 3−x . No sure conclusion could be drawn for the stoichiometry of CaMnO 3 obtained, under the same annealing conditions, from a mixture milled for longer time (150 h). No synthesis of CaMnO 3 could be effected by long (48 h) annealing at 1200 °C of mixtures that had not been subjected to mechanical stress.

The complex [Cu(en) 2 (H 2 O)](sy) 2 (en)(H 2 O) 2 has been synthesized and characterized by its electronic and vibrational spectra. The molecular structure of the complex has been determined by X-ray diffraction methods. The complex crystallizes in the orthorhombic space group Pnma with unit-cell parameters a =10.7236(5), b= 20.4660(10), c= 14.4523(11) Å and Z=4. In the cation, the Cu(II) ion has a distorted square pyramidal coordination with two bidendate (en) ligands forming the basal plane and a H 2 O molecule in the apical position. The complex cations and syringate anions constitute chains along the b axis in -A-B-A- fashion. The members of the chains are linked by through N-H ···O hydrogen bonds. The (en) molecules are responsible for connecting adjacent layers.

3-O-Benzyl-6-deoxy-1,2-O-isopropylidene-6-(dimethylaminomethylene)-α-D-xylo-hept-5-ulofuranurononitrile (1) was reacted with amidinium salts, S-methylisothiouronium sulfate, and guanidinium chloride, respectively, in the presence of bases to furnish the 4-(3-O-benzyl-1,2-O-isopropylidene- α-D-xylo-tetrofuranos-4-yl)pyrimidine-5-carbonitriles 2 and the 4-(1,2-O-isopropylidene- α-D-glycero-tetr-3-enofuranos-4-yl)pyrimidine-5-carbonitriles 3, respectively. Treatment of 1 with ethyl 5-aminopyrazole-4-carboxylates yielded the ethyl 7-(3-O-benzyl-1,2-O-isopropylidene- α-D-xylo-tetrofuranos-4-yl)-6-cyanopyrazolo[1,5-a]pyrimidine-3-carboxylates 4 and the ethyl 7-amino-6-(3-O-benzyl-1,2-O-isopropylidene-α-D-xylo-pentofuranuronoyl)pyrazolo[1,5-a]pyrimidine- 3-carboxylates 5, respectively. Reaction of 1 with 2-benzimidazolylacetonitrile in the presence of sodium methanolate afforded 1-amino-2-(3-O-benzyl-1,2-O-isopropylidene-α-D-xylo-pentofuranuronoyl) benzo[4,5]imidazo[1,2-a]pyridine-4-carbonitrile (6) and 1-amino-2-(3-deoxy-1,2-O-isopropylidene- α-D-glycero-pent-3-enofuranuronoyl)benzo[4,5]imidazo[1,2-a]pyridine-4-carbonitrile (7).

By irradiation of methyl phenylglyoxylate (1) in benzene solution in presence of equimolar amounts of 2-aminopropenenitriles H 2 C=C(NR 2 )CN (3a - e, NR2 = morpholino, 1-pyrrolidinyl, 1-piperidinyl, hexamethyleneimino, heptamethyleneimino) the corresponding 2R ∗ ,3R ∗ head-to-head oxetanes 4a - e were obtained in moderate yields (11 - 52%) along with 2 - 28% of rac-dimethyl 2,3- diphenyltartrate (2). In presence of (S)-2-(2-methoxymethylpiperidin-1-yl)propenenitrile ((+)-3g) 1 is transformed into 26% of 2 and 33% of a mixture of diastereomeric oxetanes 4g,4’g in a ratio of 1.4 : 1 which could be improved to 2.5 : 1 by preparative layer chromatography. The absolute configuration of the major diastereomer 4g was unambiguously confirmed by a single crystal X-ray structure determination to be 2R,3R,2’S. Analogous photoadditions to benzil (5a), 4,4’-bis-(trifluoromethyl)benzil (5b) and 4,4’-dichlorobenzil (5c) with (+)-3g and its lower homologue (S)-2-(2-methoxymethylpyrrolidin- 1-yl)propenenitrile ((-)-3f) gave oxetanes only in low yield as detected by 1 H NMR. Byproducts arise from competitive symmetrical α-cleavage of 5.

Heating of squaric acid (1) with the 1-aryl-3-methyl-5-oxo-2,5-dihydro-1H-pyrazoles 3a - j and the 1,3-disubstituted pyrazolinones 7a - d in the molar ratio of 1:2 in a mixture of n-BuOH/toluene afforded the bis(pyrazolyl)-squaraines 4a - j and 8a - d, respectively. Reaction of an excess of 1 with the pyrazolinone 3j yielded 4j and the 3-hydroxy-4-pyrazolyl-cyclobutene-1,2-dione 6 as a byproduct. In contrast to disubstituted pyrazolinones, the trisubstituted pyrazolinones 9a - e reacted with squaric acid (1) to give the hydroxy-oxopyrazolyl-cyclobutenediones 10a - e.

Guided by chemical screening, two new members of the antimycin group, urauchimycin C (1b) and D (1a), were isolated from the marine-derived Streptomyces sp. isolate B1751 and from a terrestrial strain AdM21, together with prefluostatin (2), a new natural derivative of isoprekinamycin (4). Their structures were established on the basis of NMR data and by comparison with known compounds. In the agar diffusion test, urauchimycin C (1b) and D (1a) were antibiotically inactive against some bacteria and fungi at a concentration of 25 μg per paper disk, while the isoprekinamycin derivative 2 showed weak cytotoxicity and moderate activity in the agar diffusion test against Bacillus subtilis, Mucor miehei, Escherichia coli and Staphylococcus aureus at concentrations of 20 μg per paper disk.

Alcohols were converted to the corresponding THP, THF or TMS ethers in high to excellent yields in 1-n-butylpyridinium chloroferrate media as a stable and low cost room temperature ionic liquid. In addition, oxidation of these ethers to their aldehydes or ketones without any overoxidation reactions in this ionic liquid was also performed.

A simple method for the oxidative aromatization of Hantzsch 1,4-dihydropyridines to the corresponding pyridines is reported using urea-hydrogen peroxide/maleic anhydride in acetonitrile.

5-(6-Chloropyridin-3-yl methyl)-4-phenyl-1,2,4-triazole-3-thiol (2) and 5-substituted-4-phenyl- 1,2,4-triazole-3-thiols (3) were synthesized. Alkylation and aminomethylation reactions of these triazoles were also carried out. Some of the newly synthesized compounds were screened for their antibacterial activities.

The new silicide NbPdSi was prepared by melting the elements in an arc-furnace.Well-shaped single crystals were obtained by annealing the sample in an induction furnace. The structure of NbPdSi has been studied by X-ray powder and single crystal diffractometer data: TiNiSi type, Pnma, Z = 4, a=643.0(1), b=376.7(1), c=744.4(2) pm, wR2=0.0330, 346 F 2 values, and 20 variables. The palladium and silicon atoms build up a three-dimensional [PdSi] network where each palladium atoms has a strongly distorted tetrahedral silicon coordination at Pd-Si ranging from 242 to 250 pm. The niobium atoms fill channels left in the [PdSi] network.

Well crystallized lepidocrocite (γ-FeOOH) with high phase purity can be prepared by precipitation from homogeneous solution. FeCl 2 is oxidized with NaClO 3 while heating the common solution slowly from 20 to 75 °C. Due to the buffer pyridine/HCl the pH-value changes only from 6.3 to 5.3. The product with the specific surface of about 16 m 2 /g has been characterized by several methods, especially by thermal analysis.

Well-shaped, small single crystals of the NdNiO 3 perovskite were grown under high oxygen pressure conditions in a belt-type press at 4 GPa. The reaction took place in sealed platinum capsules in the presence of KClO 3 as oxidizing agent. It seems that the choice of hydroxides of the involved cations as precursor reagents is crucial for the success of the crystal growth, via water vapor transport reactions. NdNiO 3 was investigated by X-ray powder and single crystal diffraction at 123 and 292 K: GdFeO 3 type, Pbnm, a = 538.10(7), b = 537.91(7), c = 760.26(10) pm, wR2 = 0.0434, 338 F 2 values, and 29 variables at 292 K. The lowtemperature data gave no hint for a monoclinic distortion: Pbnm, a = 537.91(8), b = 538.49(8), c = 760.02(12) pm, wR2=0.0299, 338 F2 values, and 29 variables. At room temperature, the Ni-O distances vary from 193.9 to 194.2 pm, and the O-Ni-O angles cover the range from 89.5 to 90.5°. Similar small distortions are observed for the NiO 6 octahedra at 123 K. Due to the strong orthorhombic distortion, the neodymium atoms have only nine oxygen neighbors at Nd-O distances from 236.0 to 295.7 pm.