Microwave Michaelis–Becker synthesis of diethyl phosphonates,tetraethyl diphosphonates,and their total or partial dealkylation

Diethyl phosphonates and tetraethyl alkyldiphosphonates were efficiently and rapidly prepared via the Michaelis–Becker reaction, under microwave irradiation. These compounds were then hydrolyzed to phosphonic and diphosphonic acids or selectively monodealkylated to give monoesters of phosphonic acids and symmetrical diethyl esters of diphosphonic acids. These reactions were also achieved rapidly in satisfactory yields with microwave methodology. This methodology was applied with success to the functionalization of a polymer resin. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:369–377, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20561     

Channel architecture via self assembly of oxamide oximes complexes

The nickel(II) and palladium(II) complexes of oxamide oximes substituted with alkyl chains of different length (C4-C8) were synthesized from the reaction of dichloroglyoxime with the corresponding amine derivatives. All compounds have been characterized by X-ray diffraction on single crystals and were found to be centrosymmetric at the metal center which is bound by the four oximic nitrogen atoms of two ligands in a square planar environment. Crystal structure analyses of Ni(II) and Pd(II) complexes showed that all of the Pd(II) complexes but only the hexyl-substituted oxamide oxime Ni(II) complex form infinite tubular channels. Their conformational analyses were carried out in order to understand the role of the chain length and of the metal center in the formation of the tubular channels and it was found that the formation of infinite tubular channels in crystals of Ni(II) and Pd(II) alkyl-substituted oxamide oxime complexes is related to the orientation of the alkyl chains relative to the central core.     

Deprotonative metalation of five-membered aromatic heterocycles using mixed lithium-zinc species

Deprotonation of benzoxazole, benzothiazole, benzo[b]thiophene, benzo[b]furan, N-Boc-protected indole and pyrrole, and N-phenylpyrazole using an in situ mixture of ZnCl(2).TMEDA (0.5 equiv) and lithium 2,2,6,6-tetramethylpiperidide (1.5 equiv) in THF at room temperature is described. The reaction was evidenced by trapping with iodine, regioselectively giving the expected functionalized derivatives in 52-73% yields. A mixture of mono- and disubstituted derivatives was obtained starting from thiazole. Cross-coupling reactions of 2-metalated benzo[b]thiophene and benzo[b]furan with heteroaromatic chlorides proved possible under palladium catalysis. A reaction pathway where the lithium amide and zinc diamide present in solution behave synergically was proposed for the deprotonation reaction, taking account of NMR and DFT studies carried out on the basic mixture.     

Vinylic Trifluoromethylselenolation via Pd-Catalyzed C−H Activation

Trifluorometylselenolation via C−H activation is barely described in literature. In particular, no such vinylic functionalization has been yet described. Herein, a palladium-catalyzed trifluoromethylselenolation of vinylic C−H bonds is described. The 5-methoxy-8-aminoquinoline has been used as auxiliary directing group to perform this reaction. The reaction gives excellent yields with α-substituted compounds whatever the substituents and a microwave activation can be used to accelerate the reaction. With β-substituted substrates lower yields, but still satisfactory, are obtained. This methodology was also successfully extended to other fluoroalkylselenyl groups.     

Synthesis,Characterization, and Energetic Properties of Salts of the 1-Cyanomethyl-1,1-dimethylhydrazinium Cation

1,1-Dimethylhydrazine can be readily alkylated with bromoacetonitrile to form 1-cyanomethyl-1,1-dimethylhydrazinium bromide ([(CH₃)₂N(CH₂CN)NH₂]Br, 1 ). The metathesis reaction of compound 1 led to the formation of a new family of energetic salts based on the [(CH₃)₂N(CH₂CN)NH₂]⁺ cation and nitrate ( 2 ), perchlorate ( 3 ), azide ( 4 ), 5-aminotetrazolate ([H₂N-CN₄]⁻, 5 ), 5,5′-azobistetrazolate ([N₄C-NN-CN₄]²⁻, 7 ), and picrate ( 8 ) anions. The new materials were characterized by elemental analysis, mass spectrometry, and (multinuclear) NMR and vibrational (infrared and Raman) spectroscopies. Additionally, the molecular structure of the [(CH₃)₂N(CH₂CN)NH₂]⁺ cation in compounds 1 , 3 , and 8 and that of sodium 5,5′-azobistetrazolate octahydrate (NaZT⋅8 H₂O) were solved by X-ray diffraction techniques. The hydrogen-bonding networks found in the structure of salts 1 , 3 , 8 , and NaZT⋅8 H₂O are described using graph-set analysis. The melting and decomposition points of the new compounds were determined by differential scanning calorimetry, and insight into their sensitivity towards impact, friction, and electrostatics was gained by submitting the materials to standard tests. Furthermore, we estimated some performance parameters of interest and predicted the decomposition gases formed upon decomposition of salts 2 , 3 , 4 , 5 , 6 , 7 , 8 and of mixtures with an oxidizer. The interesting thermal, sensitivity, and performance properties of some of the compounds described in this work make them attractive towards a prospective energetic application.     

Electron quantum optics in ballistic chiral conductors

The edge channels of the quantum Hall effect provide one dimensional chiral and ballistic wires along which electrons can be guided in an optics‐like setup. Electronic propagation can then be analyzed using concepts and tools derived from optics. After a brief review of electron optics experiments performed using stationary current sources which continuously emit electrons in the conductor, this paper focuses on triggered sources, which can generate on‐demand a single particle state. It first outlines the electron optics formalism and its analogies and differences with photon optics and then turns to the presentation of single electron emitters and their characterization through the measurements of the average electrical current and its correlations. This is followed by a discussion of electron quantum optics experiments in the Hanbury‐Brown and Twiss geometry where two‐particle interferences occur. Finally, Coulomb interactions effects and their influence on single electron states are considered.     

Novel heteroleptic heterobimetallic alkoxide complexes as facile single-source precursors for Ta(5+) doped TiO(2)-SnO(2) nanoparticles

The nanometric mixed tin-titanium oxide doped with a M(5+) cation was recently shown as a promising thermoelectric material. We report here synthesis of novel molecular precursors for above material using a convenient approach of reacting a metal chloride with a metal alkoxide. Heterometallic complexes with simple addition formula [(EtOH)(2)(OEt)(2)Ti(μ-OEt)(2)SnCl(4)] (1·EtOH) and [(EtOH)(OEt)(3)Ta(μ-OEt)(2)SnCl(4)] (2) were isolated in quantitative yield, which on recrystallization from isopropanol afforded mixed-alkoxide complexes [(Pr(i)OH)(2)(OPr(i))(2)Ti(μ-OEt)(2)SnCl(4)] (3) and [(Pr(i)OH)(OPr(i))(3)Ta(μ-OEt)(2)SnCl(4)] (4), respectively, thus indicating the robustness of the heterometallic M(μ-OEt)(2)Sn core in the solution phase. Facile conversion of these precursors to halide-free spinodal form of Ta(5+)-doped TiO(2)-SnO(2) as a potential thermoelectric material is reported.     

Direct Synthesis of Hexagonal NaGdF4 Nanocrystals from a Single‐Source Precursor: Upconverting NaGdF4:Yb3+,Tm3+ and Its Composites with TiO2 for Near‐IR‐Driven Photocatalysis

A novel single‐source precursor NaGd(TFA)₄(diglyme) (TFA=trifluoroacetate) was synthesized, characterized thoroughly, and used to obtain the hexagonal phase of NaGdF₄ nanoparticles as an efficient matrix for lanthanide‐doped upconverting nanocrystals (NCs) that convert near‐infrared radiation into shorter‐wavelength UV/visible light. These NCs were then used to prepare well‐characterized TiO₂@NaGdF₄:Yb³⁺,Tm³⁺ nanocomposites to extend the absorption range of the TiO₂ photocatalyst from the UV to the IR region. While the visible/near IR part of the photoluminescent spectra remains almost unaffected by the presence of TiO₂, the UV part is strongly quenched due to the absorption of TiO₂ above its gap at approximately 380 nm by energy transfer or FRET. Preliminary results on the photocatalytic activity of the above obtained nanocomposites are presented.