氟催化废弃硅基还原剂与CO2还原转化反应

CO2是最重要的可再生碳源之一.为了将CO2转化为有用的有机化合物,我们研究了二种模型硅基"废"材料—乙硅烷和硅粉的反应活性.在这些反应中,氟盐的催化活性最高,在常压、在质子源水和硅基还原剂的存在下,CO2可转化为甲酸.原位NMR和动力学分析表明,含氢硅烷和五配位的硅物种分别是反应中间物和活性物种.     

Synthesis of silafluorenes by iridium-catalyzed [2 + 2 + 2] cycloaddition of silicon-bridged diynes with alkynes

[reaction: see text] Silicon-bridged 1,6-diynes underwent [2 + 2 + 2] cycloaddition with alkynes in the presence of an iridium(I)-phosphine catalyst to afford densely substituted silafluorene derivatives. Extended silafluorene skeletons were constructed by the [2 + 2 + 2] cycloaddition of tetraynes.     

Stereospecific Pd‐Catalyzed Intermolecular C(sp3)–C(sp) Cross‐Coupling of Diarylmethyl Carbonates and Terminal Alkynes Under Base‐Free Conditions

A palladium‐catalyzed intermolecular decarboxylative C(sp³)–C(sp) coupling of diarylmethyl carbonates and terminal alkynes has been developed. The reaction proceeds smoothly under external base‐free conditions to deliver the corresponding alkynylated diarylmethanes with the liberation of CO₂ and MeOH as the sole byproducts. Moreover, enantioenriched diarylmethyl carbonates are stereospecifically converted to optically active cross‐coupling products with inversion of configuration. Thus, the stereospecific palladium catalysis can provide new and unique access to the alkynylated chiral tertiary stereocenters, which are relatively difficult to construct by conventional methods.     

Iron content and temperature dependences of diffuse scattering in Ti–(50–x)Ni–xFe (6 ≤ x ≤ 10) alloys

Diffuse scatterings appearing in electron diffraction patterns of Ti–(50???x)Ni–xFe (x?=?6, 7, 8, 10, in at.%) alloys were investigated. In the alloys, martensitic (R-phase) transformation is suppressed down to 4.2 K, but the electrical resistivity exhibits a local minimum at T _min (210 K, 195 K, 180 K and 140 K for x?=?6, 7, 8, 10, respectively). The following results were obtained for all the alloys. Diffuse scattering appears below T _min and its intensity maximum is located at an incommensurate position of g?+??ζζ0?*, where g is a reciprocal lattice vector of the B2-phase. The value?ζ?at T _min is significantly smaller than 1/3 and increases with decreasing temperature; it decreases with increasing Fe content. The value of?ζ?at T _min agrees with the length of nesting vector obtained by a band calculation, suggesting that the diffuse scattering is caused by the nesting effect of the Fermi surface in the B2-type structure.     

Lanthanum(III) isopropoxide catalyzed chemoselective transesterification of dimethyl carbonate and methyl carbamates

A practical transesterification of less reactive dimethyl carbonate and much less reactive methyl carbamates with primary (1°), secondary (2°), and tertiary (3°) alcohols was established with the use of a lanthanum(III) complex, which was prepared in situ from lanthanum(III) isopropoxide (3 mol %) and 2-(2-methoxyethoxy)ethanol (6 mol %). In particular, corresponding carbonates and carbamates obtained were of synthetic utility from the viewpoint of the selective protection and/or deprotection of 1°-, 2°-, and 3°-alcohols.     

Deprotonation‐Induced Aromaticity Enhancement and New Conjugated Networks in meso‐Hexakis(pentafluorophenyl)[26]hexaphyrin

meso‐Hexakis(pentafluorophenyl)‐substituted neutral hexaphyrin with a 26π‐electronic circuit can be regarded as a real homolog of porphyrin with an 18π‐electronic circuit with respect to a quite flat molecular structure and strong aromaticity. We have investigated additional aromaticity enhancement of meso‐hexakis(pentafluorophenyl)[26]hexaphyrin(1.1.1.1.1.1) by deprotonation of the inner N? H groups in the macrocyclic molecular cavity to try to induce further structural planarization. Deprotonated mono‐ and dianions of [26]hexaphyrin display sharp B‐like bands, remarkably strong fluorescence, and long‐lived singlet and triplet excited‐states, which indicate enhanced aromaticity. Structural, spectroscopic, and computational studies have revealed that deprotonation induces structural deformations, which lead to a change in the main conjugated π‐electronic circuit and cause enhanced aromaticity.     

Strained and unstrained macrocycles composed of carbazole and butadiyne units: electronic state and optical properties

Cu(OAc)(2) catalyzes dehydrogenative condensation of 3,6-bis(2-ethynylphenyl)carbazole in the presence of O(2) to afford the cyclization product 1 and cyclodimer 2. Compound 1 contains bent carbazole and butadiyne groups, while 2 has a less strained structure with Z shape around the two parallel butadiyne groups. Optical properties of the compounds are discussed based on the electronic states estimated from electrochemical measurement and density functional theory calculation.     

Facile synthesis of rhodium and iridium complexes bearing a [PEP]-type ligand (E = Ge or Sn) via E-C bond cleavage

Rhodium and iridium complexes bearing a tridentate [PEP] type ligand ([PEP] = {o-(Ph(2)P)C(6)H(4)}(2)E(Me); E = Ge or Sn) were synthesized through the phosphine exchange reaction accompanied by selective E-C bond cleavage. The ligand precursors {o-(Ph(2)P)C(6)H(4)}(2)EMe(2) (E = Ge or Sn) were readily obtained in excellent yields by treating {o-(Ph(2)P)C(6)H(4)}(2)Li with 0.5 equivalents of Me(2)ECl(2). Tris(triphenylphosphine)rhodium(i) carbonyl hydride M(H)(CO)(PPh(3))(3) (M = Rh, Ir) cleaved one of the E-Me bonds of {o-(Ph(2)P)C(6)H(4)}(2)EMe(2) exclusively to afford the trigonal bipyramidal (TBP) complexes, [PEP]M(CO)(PPh(3)). Square-planar rhodium complexes [PEP]Rh(PPh(3)) were also prepared from the reactions of tetrakis(triphenylphosphine)rhodium(i) hydride Rh(H)(PPh(3))(4) with {o-(Ph(2)P)C(6)H(4)}(2)EMe(2). Further, the trans influence of group 14 elements E (E = Si, Ge, Sn) in [PEP]Rh(PPh(3)) is discussed in terms of the (1)J(Rh-P) coupling constants, indicating that E exhibited a stronger trans labilizing effect in the order Sn < Ge < Si.     

Synthesis of iridium complexes bearing {o-(Ph2P)C6H4}(3)E type (E = Si, Ge, and Sn) ligand and evaluation of electron donating ability of group 14 elements E

Trigonal bipyramidal (TBP) iridium(i) complexes {o-(Ph(2)P)C(6)H(4)}(3)EIr(CO) (E = Si: 1-Ir, Ge: 2-Ir, Sn: 3-Ir) comprising group 14 element E were synthesized and converted into the corresponding cationic iridium(III) complexes [{o-(Ph(2)P)C(6)H(4)}(3)EIr(H)(CO)][BF(4)] (E = Si: 4, Ge: 5, Sn: 6) bearing octahedral geometry by protonation using (Et(2)OH)(BF(4)). The origin of trans-labilizing abilities of E was investigated through structural analysis, IR and NMR spectroscopic analysis, and density functional theory calculations. Further, the electron-donating abilities of E were investigated through proton transfer reactions.     

Composite and Elementary Components in Hadron Resonances

In hadron resonances different structures of hadronic composite (molecule) and elementary (quark-intrinsic) natures may coexist. We sketch discussions based on our previous publications on the origin of hadron resonances (Hyodo et al. Phys. Rev. C 78:025203, 2008) on exotic ${\bar D (B)}$ meson–nucleons as candidates of hadronic composites (Yamaguchi et al. Phys. Rev. D 84:014032, 2011) and on a ₁ for the coexistence/mixing of the two different natures (Nagahiro et al. Phys. Rev. D 83:111504, 2011).