Beryllium-9 NMR Spectroscopy and Molecular Orbital Studies of Hydrogen-Bonding Interaction of Tetraaquaberyllium(II) Ion with Water in the Second Solvation Sphere in Propiononitrile

The equilibrium constants of the hydrogen-bonding interactions between the tetraaqua-beryllium(II) ion ([Be(H₂O)₄]²⁺) and water in the second solvation sphere were determined from the dependence of the ⁹Be NMR chemical shift (δ_Be) on the water concentration (C _W) in propiononitrile (PN). The ⁹Be NMR line assigned to [Be(H₂O)₄]²⁺ is downfield shifted with the increasing C _W, and the change in δ_Be as a function of C _W is explained in terms of a two-step hydrogen-bonding interaction to form [Be(H₂O)₄](H₂O) _n ²⁺ (n = 1, 2). Molecular orbital calculations for [Be(H₂O)₄](H₂O) _n ²⁺ (n = 0?2) revealed that the electron density on the Be(II) ion increases with an increase in n due to an enhanced polarization of the bound water molecules accompanied by the hydrogen bonding in the second solvation sphere. The observed downfield shift of δ_Be is interpreted as a significant compensation of the diamagnetic upfield shift by the paramagnetic contribution due to the mixing of the vacant s and p orbitals of Be with the σ-type lone-pair orbitals of the coordinating water molecules.     

A 1H NMR study of the effects of Ni additions on the behavior of hydrogen in β-vanadium hydride

The behavior of hydrogen in the hydrides of vanadium metal containing small amounts of nickel was studied by ¹H NMR spectroscopy. FT spectra and spin-spin and spin-lattice relaxation times for VH_0.77, V_0.95Ni_0.05H_0.73, and V_0.90Ni_0.10H_0.65 were measured at temperatures between 77 and 400 K. On the addition of nickel the number of hydrogen atoms on O₂₂ sites decreases and the superstructure of hydrogen is altered. Different effects of nickel on hydrogen diffusion are observed above and below about 200 K, and, therefore, the mechanism of hydrogen diffusion is assumed to change at this temperature.     

Porphyrin derivatives act as vinylene monomers in TEMPO‐mediated radical copolymerization with styrene

In this article, we offer clear evidence for the radical copolymerizability of porphyrin rings in 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)‐mediated radical copolymerizations with styrene. The radical copolymerizations of styrene with 5,10,15,20‐tetrakis(pentafluorophenyl)porphyrin (H₂TFPP) was conducted using 1‐phenyl‐1‐(2,2,6,6‐tetramethyl‐1‐piperidinyloxy)ethane as an initiator. The refractive index (RI) traces for the size‐exclusion chromatography of the resulting copolymers were unimodal with narrow molecular weight distributions. The RI traces shifted toward higher molecular weight regions as the polymerization progressed, and the number‐average molecular weights were close to those calculated on the basis of the feed compositions and monomer conversions. These features were in good agreement with a TEMPO‐mediated mechanism. The traces recorded by the ultraviolet‐visible (UV‐vis) detector (430 nm) were identical to those obtained by the RI detector, indicating a statistical copolymerization of styrene with H₂TFPP. This also indicated that H₂TFPP acted as a monomer and not as a terminator or a chain‐transfer agent under the conditions used. A benzyl radical addition to H₂TFPP was conducted as a model reaction for the copolymerization using tributyltin hydride as a chain‐transfer agent, affording a reduced porphyrin, 2‐benzyl‐5,10,15,20‐tetrakis(pentafluorophenyl)chlorin 1 , via radical addition to the β‐pyrrole position. The UV‐vis spectrum of 1 was fairly similar to that of poly(styrene‐co‐H₂TFPP), indicating that H₂TFPP polymerized at its β‐pyrrole position in the TEMPO‐mediated radical polymerization. TEMPO‐mediated radical copolymerizations of styrene with several porphyrin derivatives were also demonstrated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Chiral Brønsted Acid Catalyzed Enantioconvergent Propargylic Substitution Reaction of Racemic Secondary Propargylic Alcohols with Thiols

Despite the significant progress of the enantioselective reaction using chiral catalysts, the enantioselective nucleophilic substitution reaction at the chiral sp³-hybridized carbon atom of a racemic electrophile has not been largely explored. Herein, we report the enantioconvergent propargylic substitution reaction of racemic propargylic alcohols with thiols using chiral bis-phosphoric acid as the chiral Brønsted acid catalyst. The substitution products were formed in high yields with high enantioselectivities in most cases. The cation-stabilizing effect of the sulfur functional group introduced at the alkynyl terminus is the key to achieving the efficient enantioconvergent process, in which chiral information originating from not only the racemic stereogenic center but also the formed contact ion pair is completely eliminated from the present system.     

Synthesis and crystal structures of phenylalanine ester-introduced palladium(II) and platinum(II) complexes and their cytotoxicities

Research on Chemical Intermediates - Phenylalanine ester-introduced palladium(II) and platinum(II) complexes were synthesized. Taking advantage of the formation of Schiff bases by amino acids as an...     

Aerobic oxidative homocoupling reaction of anilides using heterogeneous metal catalysts

We have developed a heterogeneous catalytic oxidative homocoupling reaction of dimethoxyanilides under an oxygen atmosphere. The resulting homo-dimers are useful for the construction of heterocycles, demonstrating the potential of heterogeneous metal catalysts.     

Mitochondrial mode of action of a thymidine-based cisplatin analogue breaks resistance in cancer cells

Cisplatin analogue complexes with platinum(II) and palladium(II) starting from 3',5'-diamino-3',5'-dideoxy-thymidines were synthesized, both with the D-erythro- and D-threo configurations. Complexes of the general formula [MCl(2)L] were obtained and characterized. NMR spectroscopic measurements and single crystal X-ray structure analysis showed that the metal centers are coordinated to the ligands by the amino groups in 3'- and 5'-positions and not through the thymine moiety. All ligands and complexes showed no significant in vitro activities except thymiplatin (cis-dichloro(3',5'-diamino-3',5'-dideoxy-D-threo-thymidine)platinum(II)). Detailed in vitro studies on the apoptosis pathway in lymphoma (BJAB), leukemia (NALM-6), and melanoma cells (Mel-HO) as well as on transfected or resistant cell lines were carried out. Thymiplatin significantly induced an apoptotic response, which was found to be associated with the loss of mitochondrial membrane potential and with caspase activation. The activity was shown to be independent of Fas-associated protein with death domain (FADD), but dependent on Bcl-2 expression. As a consequence, for thymiplatin a mitochondrial mode of action could be assigned. Moreover, the compound showed activity in cells resistant to common drugs, such as daunorubicin and vincristin, and showed synergistic effects with doxorubicin, vincristin, cytarabin, and daunorubicin.     

Dopaldehyd: erstmalige Isolierung aus einer Pflanze in Form seines (Z)-Enol-(E)-Kaffeesäureesters

Dopaldehyd (homoprotocatechu aldehyd; 3,4-dihydroxyphenyl acetaldehyd), in form of its (Z)-enol-(E)-caffeic ester, has been detected for the first time as a natural occurring compound. It is a constitutent of the yellow pigments of the glands on the leaves of Plectranthus caninus ROTH (Labiatae).     

Novel generation of (α-ketovinyl)thioketenes as intermediates through tandem [2,3]/[3,3] sigmatropic rearrangement of alkynyl propargyl sulfoxides

Thermal reaction of alkynyl propargyl sulfoxides 1 afforded novel highly reactive (α-ketovinyl)thioketenes 3. Trapping experiments using a primary or secondary amine, formation of furanophane 4, through head-to-tail type dimerization, as well as direct observation using ¹H NMR elucidated the generation pathway of 3 through sequential [2,3]/[3,3] sigmatropic rearrangement.