Orientation of the imidazole type ligands in copper complexes studied by ESEEM

Effects of nitrogen quadrupole coupling tensors on ESEEM spectra are discussed. It is shown from theoretical considerations that the spectra, especially the double quantum transition line, are strongly affected by changes of tensor orientation in the magnetic field. Model calculations for angle-selected nitrogen ESEEM spectra of copper complexes in the disordered state show that the double quantum transition line changes its intensity with the resonance magnetic field set position in the EPR spectrum. These model calculations also show that estimation of the orientation of the imidazole type ligands with respect to theg principal axes may be easily made without any tedious processes of computer simulation of the whole ESEEM spectral pattern. The usefulness of the method is experimentally shown by applying it to the structural studies of the copper complexes of 2-(2′-pyridyl)imidazole and 2(2′-pyridyl) benzimidazole and their six coordinated complexes with nitrogeneous bases.     

N-H insertion reactions of primary ureas: the synthesis of highly substituted imidazolones and imidazoles from diazocarbonyls

Primary ureas have been used as substrates in rhodium-catalyzed N-H insertion reactions with an array of diazocarbonyls. The insertion reaction is efficient and gives excellent selectivity and yields. The products from the insertion reaction with diazoketones cyclize readily in the presence of acid to yield the corresponding imidazolones that can be further derivatized by N-alkylation with alkyl, allyl, and benzyl halides. Alternatively, the imidazolones were treated with phosphorus oxybromide to form the corresponding 2-bromoimidazoles that were further functionalized using a Suzuki coupling reaction.     

Iron-catalyzed cross-coupling of alkenyl sulfides with Grignard reagents

[reaction: see text] The iron-catalyzed cross-coupling reaction of alkenyl sulfides with Grignard reagents is described. While the cross-coupling proceeds efficiently at alkenyl-S bonds, almost no cross-coupling takes place at aryl-S bonds, attesting to a unique selectivity of iron catalysis. The beneficial effect of potentially coordinating 2-pyrimidyl group on sulfur is also described.     

Total synthesis, elucidation of absolute stereochemistry, and adjuvant activity of trihydroxy fatty acids

Pinellic acid from the tuber of Pinellia ternate, an active herbal component of the traditional Japanese herbal (Kampo) medicine Sho-seiryu-to, is a C18 trihydroxy fatty acid whose absolute stereochemistry has now been determined. All stereoisomers of pinellic acid were synthesized via regioselective asymmetric dihydroxylation, regioselective inversion, and stereoselective reduction in order to determine their absolute stereochemistries and adjuvant activities. Among this series of isomers, the (9S,12S,13S)-compound, which is a natural product, exhibited the most potent adjuvant activity. Spectral data for all of the stereoisomers of the 1,2-allylic diols were compared and related to their stereochemistries.     

Enone Synthesis via Palladium Catalyzed Reductive Carbonylation of Terminal Acetylenes

Aryl vinyl ketones are prepared by the reaction of aryl iodides and terminal acetylenes in the presence of a catalytic amount of PdCl₂(PPh₃)₂, Cp₂TiCl₂ and a stoichiometric amount of Zn-Cu under an atmospheric pressure of carbon monoxide.     

Improved photoelectrochemical performance of electrodeposited ZnO/EosinY hybrid thin films by dye re-adsorption

Dye desorption and re-adsorption post treatments on electrochemically self-assembled nanoporous ZnO/eosinY hybrid thin films lead to a large improvement of the dye-sensitized photoelectrochemical performance, achieving an incident photon to current conversion efficiency up to 90%.     

Desorption of InOH from indium oxides under exposure to atomic hydrogen

Species desorbing from indium oxides under exposure to atomic hydrogen (H) were observed with a quadrupole mass spectrometer. The desorption of InOH was detected at a temperature as low as 410°C, which is in contrast with the fact that, with molecular hydrogen, a much higher temperature (850°C) was required to generate InOH. Upon the interruption of H generation, the InOH signal disappeared immediately, suggesting that H is involved in the reactions leading to InOH desorption. Relevance to the low-temperature cleaning of an InP surface with H is discussed.     

Synthesis of panax acetylenes: chiral syntheses of acetylpanaxydol, PQ-3 and panaxydiol

Acetylpanaxydol (1-Ac), PQ-3 (2) and panaxydiol (3) and their optical isomers were synthesized from L-(+)-diethyl tartrate. The absolute configurations of 1-Ac, 2 and 3 were determined to be 1-Ac (3R,9R,10S), 2 (9R,10S) and 3 (3R,10S), respectively, by comparisons of their optical rotations and the NMR data of their MTPA esters with those of natural products.