C - axis resistivity of stages 1–7 potassium-intercalated graphite

Temperature-dependent c-axis resistivity measurements on stages 1–7 potassium-graphite compounds show a crossover from metallic to activated behaviour between stages 4 and 5, as well as the onset of a new type of anomaly for stage ≥4. KC₈ shows in addition a tendency toward a metal-insulator transition below 40K. The high-stage transport process is discussed in terms of weak depletion of the interior layers by interlayer screening. We suggest that the high stage anomalies reflect an instability in the c-axis charge distribution.     

Study of the isomeric ratios in photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We have determined the isomeric ratios in ¹⁶⁵Ho(γ, n)^164m,gHo and ¹⁷⁵Lu(γ, n)^174m,gLu photonuclear reactions of natural holmium and lutetium induced by bremsstrahlungs with end-point energies in the giant dipole resonance (GDR) region. The investigated samples were irradiated at electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reaction, Joint Institute for Nuclear Research, Dubna, Russia. The gamma spectra of the samples irradiated were measured with spectroscopic system consisting of 8192 channel analyzer and high-energy resolution (180 keV at gamma ray 1332 keV of ⁶⁰Co) HP(Ge) semiconductor detector Canberra. The GENIE2000 (Canberra) computer program was used for data processing. The results were discussed and compared with those of other authors.     

Caesaldecan, a cassane diterpenoid from the leaves of Caesalpinia decapetala

A new cassane diterpenoid, caesaldecan, was isolated from Caesalpinia decapetala with eight known compounds, spathulenol, 4,5-epoxy-8(14)-caryophyllene, squalene, lupeol, trans-resveratrol, quercetin, astragalin, and stigmasterol. The (1)H- and (13)C-NMR spectra of the new compound were completely assigned by using a combination of 2D NMR techniques, namely, (1)H-(1)H COSY, HMQC, HMBC, and ROESY.     

Reactions of 1,2,4-triazines with nitromethide ion. A convenient method of preparation of 1,2,4-triazin-5-ylcarbaldehyde oximes and their synthetic applications

An efficient procedure for the preparation of 1,2,4-triazin-5-ylcarbaldehyde oximes 2a-f from 1,2,4-triazines 1a-f and nitromethide ion is described. The oximes 2c-d were converted into corresponding 5-cyano-1,2,4-triazines 6c-d . The latter compounds react easily with various nucleophiles to afford 5-substituted 1,2,4-triazines 7a-i and with 1-pyrrolidino-1-cyclohexene to form cyano derivative of 5,6,7,8-tetrahydroisoquinoline 9 .     

Synthesis and reactivity of naphthalene sandwich complexes of molybdenum. X-ray structure of [Mo(η6-naphthalene) {P(OMe)3}3] and [Mo(H)(η6-naphthalene){P(OMe)3}3][BF4]

The sandwich complexes bis(η⁶-naphthalene)molybdenum(0) ( 1 ), bis(η⁶-1-methylnaphthalene)molybdenum(0) ( 2 ), and bis(η⁶-1,4-dimethylnaphthalene)molybdenum(0) ( 3 ) are synthesized by cocondensation of Mo-atoms with the naphthalene ligands. Complexes 1–3 are also obtained by reduction of MoCl₅ or MoCl₄. 2THF with highly activated Mg in the presence of the naphthalene ligands. Mg was activated by sublimation of the metal in a simple rotating solution reactor. Complex 2 exists as a mixture of regio- and stereoisomers. Three regioisomers, 3a–c , are formed in reactions of Mo-atoms with 1,4-dimethylnaphthalene, whereas 3a , the isomer with the Mo-atom coordinated to the unsubstituted rings, is formed selectively via the reductive method. The ligands in 1–3 are highly labile. CO displaces both naphthalene rings in 2 and 3 to give [Mo(CO)₆], while PF₃, P(OMe)₃, and PMe₃ displace only one coordinated naphthalene in 1 to yield the [Mo(η⁶-naphthalene)L₃] complexes 4–6 . In toluene, arene exchange is a competitive process in reactions of 1 with PF₃. Complexes 5 (L = P(OMe)₃) and 6 (L = PMe₃) react with HBF₄ to give the cationic metal hydride complexes 8 and 9 . The X-ray crystal structures of [Mo(η⁶-naphthalene) {P(OMe)₃}₃] ( 5 ) and [Mo(H)(η⁶-naphthalene) {P(OMe)₃}₃][BF₄] ( 8 ) are reported.     

Synthesis of 2-fluoro-6-O-propargyl-11,12-carbamate ketolides. A novel class of antibiotics

A novel class of 2-fluoro-6-O-propargyl-11,12-carbamate ketolide derivatives of erythromycin has been synthesized for antibacterial SAR studies. Replacement of the C2-hydrogen by a fluorine atom allows the synthesis of 6-O-propargylic ketones and electron-deficient 6-O-propargylic aromatic derivatives by preventing intramolecular C2-enolate Michael cyclization.