(Z)-Selective enol triflation of α-alkoxyacetoaldehydes: Application to synthesis of (Z)-allylic alcohols via cross-coupling reaction and [1,2]-wittig rearrangement

The stereoselective transformation of α-alkoxyacetoaldehydes to the corresponding (Z)-vinyl triflates was achieved by treatment with phenyl triflimide and DBU. The stereochemistry was explained by the "syn-effect," which was attributed primarily to an σ → π∗ interaction. The β-alkoxy vinyl triflates obtained were applied to the stereoselective synthesis of structurally diverse (Z)-allylic alcohols via transition metal-catalyzed cross-coupling reaction and [1,2]-Wittig rearrangement. © 2015 American Chemical Society

Anomalous Transport Properties in BiS2-based Superconductors LnO1−xFxBiS2 (Ln = Nd, La-Sm)

We report the electronic properties of the layered bismuth-based sulfide superconductors NdO1−xFxBiS2 (x = 0.25, 0.4, and 0.5) and La1−ySmyO0.5F0.5BiS2 (y = 0.1–0.7), which have been studied by investigation of their transport properties and X-ray diffraction. In the lightly carrier-doped NdO1−xFxBiS2 (x = 0.25 and 0.4) and La1−ySmyO0.5F0.5BiS2 (y = 0.3 and 0.4), the resistivity and Hall coefficient exhibit anomalous temperature dependences below TCDW ∼ 130 and 200 K, respectively, suggesting the formation of an energy gap on the Fermi surface associated with charge-density wave (CDW). In NdO1−xFxBiS2 (x = 0.25), the bond angles and bond lengths of the Bi–S pentahedron change their temperature dependences below ∼200 K, suggesting that a lattice instability related to the Bi–S pentahedron exists below ∼200 K, which is much higher than TCDW. These results indicate that the lattice instability of the Bi–S pentahedron can trigger a CDW transition in the low-carrier region of BiS2 superconductors

(<i>Z</i>)‑Selective Enol Triflation of α‑Alkoxyacetoaldehydes: Application to Synthesis of (<i>Z</i>)‑Allylic Alcohols via Cross-Coupling Reaction and [1,2]-Wittig Rearrangement

The stereoselective transformation of α-alkoxyacetoaldehydes to the corresponding (<i>Z</i>)-vinyl triflates was achieved by treatment with phenyl triflimide and DBU. The stereochemistry was explained by the “<i>syn</i>-effect,” which was attributed primarily to an σ → π* interaction. The β-alkoxy vinyl triflates obtained were applied to the stereoselective synthesis of structurally diverse (<i>Z</i>)-allylic alcohols via transition metal-catalyzed cross-coupling reaction and [1,2]-Wittig rearrangement