Measurement of the g-factor of the 0.57 ms 7+ state in202Tl

The spin rotation of the 0.57 ms 7⁺state in²⁰²Tl has been observed by use of a pulsed magnetic field and the g-factor was determined to be 0.128 ± 0.006. The isomeric state was excited via the ²⁰⁴Hg(p, 3n)²⁰²Tl reaction with a 28 MeV pulsed beam of 1.2 ms interval. From the results, the main configuration of the 7⁺ state in²⁰²Tl is interpreted as ().     

Angle-resolved photoemission of the c(2 × 2) and c(3 × 1) oxygen overlayers on Fe(110)

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the band structure of the c(2×2) and (3×1) oxygen overlayers on Fe(110). The symmetries of the O-2p-derived states at the center of the surface Brillouin zone $\text{(}\text{Γ}\text{)}$ were identified using polarized light. At $\text{Γ}$ the p_xp_y- and p_z-derived levels are at about 5.5 and 7.0 eV below the Fermi level, respectively, for both ordered overlayers. The p-states of the c(2×2)-O structure show very little dispersion (?0.1 eV) with $\text{k}{}_{\mathrm{}}$. On the other hand, the c(3×1)-O overlayer exhibits considerable dispersion of ～1.6 eV. The essential features of the measured dispersion are reproduced well by the dispersion predicted in a qualitative way for an isolated c(3×1) oxygen monolayer.     

Investigation of neutron deficient Zr and Nb nuclei with heavy ion induced compound reactions

³²S and¹²C induced compound reactions on Fe, Ni and Se targets have been used to produce neutron deficient nuclei in the mass region 84≦A ≦87. In-beamγ-ray spectroscopy consisting of the measurement of excitation functions,γγ coincidences andγ-ray angular distributions has been performed. The following level energies and spin-parity values have been deduced:⁸⁴Zr: 540 keV, 2⁺; 1262.8, (4⁺); 2137.2, (6⁺); 3089.2⁸⁶Zr: 751.9, 2⁺; 1666.6, (4⁺); 2670.0, (6⁺); 2705.5, (5); 3271.3; 3298.5, (8⁺); 3423.5, (7); 3531.5, (10⁺); 3645.9; 4326.1; 4417.3 Half-lives and energies ofγ-rays from the residual activities have been measured. The existence of three new isotopes could be established by their radioactive decay:⁸⁴Nb(12±3 s)→⁸⁴Zr⁸⁶Nb(80±12 s)→⁸⁶Zr⁸⁷Mo(14.6±1.5 s)→⁸⁷Nb→⁸⁷Zr     

Synthesis of Δ1[9]- and/or Δ8[9]-dehydroindolizidines and related compounds

A facile synthesis of Δ^1[9]- and/or Δ^8[9]-dehydroindolizidine and related compounds, consisting of dry distillation of γ-(N-2-piperidinonyl)butyric acid over soda-lime, is described. Reductions of these dehydroindolizidines and stereochemistry of 1-methylindolizidine are also described.     

Synthetic studies on taxol: highly stereoselective construction of the taxol C-ring via SN2' reduction of an allylic phosphonium salt

[reaction: see text] The highly stereoselective construction of the C3 stereogenic center of the taxol C-ring is described. The trans isomer at the C3-C8 position of the taxol C-ring, which is required for the total synthesis, as well as its diastereomeric cis isomer were successfully synthesized with highly diastereoselective S(N)2' reduction of the allylic phosphonium salts.     

Irreversible Photoinduced Insulator-Metal Transition in Charge Ordered Pr 0.75 Na 0.25 MnO 3

Irreversible photoinduced insulator-metal transition has been observed in a perovskite manganite doped with monovalent Na + , Pr 0.75 Na 0.25 MnO 3 . The increase of the conductance is estimated to be of the order of 10 4 -10 5 , considering the shallow penetration depth ( ¨ 0.1 µm) of illumination light. Analysis of the dc- and ac-susceptibility data shows that the system is in a cluster glass state below 45 K, which means that ferromagnetic metallic clusters exist in insulating matrix. The photo-excitation helps the clusters to dislodge from a local energy minimum and to seek more stable configuration. The observed large increase of the conductivity can be well explained by the percolative conduction. We argue that metastability is due to the large charge mismatch between the monovalent Na + ion and trivalent Pr 3+ ion or the deviation of the average Mn valency from 3.5+.     

Catalytic Alkynylation of Polyfluoroarenes by Amide Base Generated In Situ

We herein demonstrate that the amide base generated in situ from CsF and N(TMS)₃ catalyzes the deprotonative coupling reactions of terminal alkynes with polyfluoroarenes, wherein mono- and dialkynylations occur efficiently for penta- and hexafluorobenzenes, respectively. Tetraalkynylated products could also be synthesized from dialkynylated compounds.     

General, robust, and stereocomplementary preparation of beta-ketoester enol tosylates as cross-coupling partners utilizing TsCl-N-methylimidazole agents

We have developed a general, robust, and cost-effective method for the (E)- or (Z)-stereocomplementary enol tosylation of beta-ketoesters using TsCl- N-methylimidazole (NMI)-Et3N or LiOH. TsCl coupled with NMI formed a highly reactive N-sulfonylammonium intermediate. Stereocongested secondary alcohols were smoothly sulfonylated using Ts(Ms)Cl-NMI-Et3N. beta-Ketoesters underwent (E)-selective tosylation using TsCl-NMI-Et3N and (Z)-selective tosylation using TsCl-NMI-LiOH (total of 23 examples; 60%-99% yield). Stereoretentive Negishi and Sonogashira couplings using enol tosylates proceeded successfully to give trisubstituted alpha,beta-unsaturated esters.