Reduction of aldehydes and ketones by sodium dithionite using viologens as electron transfer catalyst

It was found that aromatic aldehydes and ketones could be reduced smoothly at room temperature by sodium dithionite using viologen derivatives as an electron transfer catalyst to obtain the corresponding alcohols in good yields. Viologens (methyl viologen and polymer) acted catalytically and active species in the reduction were quinoid forms which were obtained by two-electron reduction of viologens.     

O‐Triorganosilyl Carbamoselenoates – Synthesis and Reactions

A series of O‐triorganosilyl carbamoselenoates were isolated in good yields from the reaction of sodium or potassium carbamoselenoates with triorganosilyl chlorides. The O‐silyl carbamoselenoates readily reacted with RbF and CsF and with organo‐germanium, ‐tin, and ‐lead halides and gave the corresponding heavy alkali metal and Se‐substituted Group 14 organometal and carbamoselenoates in moderate to good yields.     

The electronic structure of the heptafulvalene trianion radical—The doublet instability of the Hartree-Fock solution and related phenomena

The restricted Hartree-Fock (RHF) solution for the trianion radical of heptafulvalene, obtained using the open-shell SCF formalism of the Pariser-Parr-Pople method, is found to be doublet unstable at the conventionalD _2h nuclear arrangement. We calculate the broken-symmetry charge-density wave (CDW) solution and examine its properties. It is shown that the proton hyperfine splittings for the trianion radical calculated from the CDW solution are in good agreement with the experimental values. Further, we briefly refer to the possibility of the lattice instability of the trianion radical from the fully-symmetricalD _2h to theC _2v nuclear arrangement.     

Asymmetric allylsilane-mediated carbocyclization: A highly enantiospecific synthesis of (1S, 2S)-(+)-2-methyl-3-cyclopenten-1-ol

An enantiospecific synthesis of the title compound is described which involves the TiCl₄-promoted cyclization of the chiral allylic silane having formyl group, which was obtained via the Claisen rearrangement of ($\text{R}$, $\text{E}$)-1-trimethylsilyl-1-buten-3-ol.     

A new ruthenium complex with an electron-donating aminoindenyl ligand for fast metal-mediated living radical polymerizations

A new ruthenium complex with an electron-donating aminoindenyl ligand induces a fast living radical polymerization of methyl methacrylate (MMA) in the presence of a chloride initiator to give polymers with controlled and variable molecular weights (Mn = 103-105) and very narrow molecular weight distributions (Mw/Mn < 1.1). The structure and high activity of the catalyst were analyzed by X-ray crystallography and cyclic voltammetry in comparison to those of a similar complex with an indenyl ligand.     

Further studies on aplyronine A, an antitumor substance isolated from the sea hare Aplysia kurodai

By a series of reactions aplyronine A (1) an antitumor substance of marine origin was transformed into six fragments, and their structures were characterized by spectroscopic methods. Relative stereochemistry of four contiguous chiral centers (C29–C32) in 1 was established and that of three contiguous chiral centers (C23–C25) in 1 was deduced on the basis of the ¹H NMR spectral analysis of the fragment 8 and the derived acetonide 9, respectively.     

Effects of preparing and ligand-binding methods of small unilamellar liposomes on their blood elimination and tissue distribution in rats

The effects of two methods of preparing small unilamellar vesicles (SUV) (detergent removal or sonication) on their in vivo elimination and tissue distribution was investigated in rats. The SUV prepared by either method had the same size distribution and lipid composition (egg yolk phosphatidylcholine/cholesterol/dipalmitoyl phosphatidylethanolamine or palmitic acid = 20/10/0.3, molar ratio). Three types of SUV made by either method were prepared. These contained one of three different surface ligand-binding functional groups (N-hydroxysuccinimide ester of palmitic acid, NHSP; glutaraldehyde-phosphatidylethanolamine, GA-PE; N-[4-(p-maleimidophenyl)butyryl]phosphatidylethanolamine, MPB-PE). SUV prepared by detergent removal were eliminated slowly from the circulation, and exhibited a low liver uptake and little leakage of [3H]inulin. There was no significant difference in elimination of the NHSP-SUV, GA-SUV or MPB-SUV prepared by detergent removal and their tissue distribution was similar. In contrast, the sonicated SUV were eliminated from the circulation much more rapidly mainly by liver uptake. The leakage of [3H]inulin from sonicated SUV into urine was relatively large. When sonicated control-SUV were prepared in the presence of the antioxidant, alpha-tocopherol (alpha-T-SUV), which reduces lipid peroxidation during sonication, the alpha-T-SUV were eliminated slowly with only a low liver uptake. Our results indicate that the rapid elimination and greater liver uptake of sonicated SUV is partly due to lipid peroxidation during preparation. These findings have relevance to the use of liposomes as a drug delivery system.     

Singlet oxygen reaction—II: Alkylthiosubstituted ethylene

The reaction of singlet oxygen with tetrakis(ethylthio)ethylene has been shown to afford diethylthiooxalate and diethyl disulfide. The expected diethylthiocarbonate was also obtained as a minor product. A similar reaction with bis(ethylthio)ethylene gave ethylthioglyoxalate together with diethyl disulfide. Formation of diethylthioacetaldehyde was also observed, and is suggested to proceed via the intermediary 1,2-dioxetane or perepoxide followed by preferential migration of the ethyltilio group. On the other hand, phenylthioethylene is oxidized with singlet oxygen to give a thiol ester together with disulfide. This suggests that the formation of disulfide probably occurs via a radical pathway. The photooxygenation of disulfide in alcohol was also studied.     

Effects of carboxyl groups on the adsorption behavior of low-molecular-weight substances on a stainless steel surface

The adsorption isotherms of various carboxylic acids and several amines on a stainless steel surface were taken as a function of pH and the ionic strength of the solution at 30 degrees C. In particular, the effect of the number of carboxyl groups on the adsorption behavior was investigated. Monocarboxylic acids such as benzoic acid and n-butyric acid were reversibly adsorbed on the stainless steel particles and showed a Langmuir-type adsorption isotherm, i.e., Q=KqmC/(1+KC), where Q and C are, respectively, the amount of adsorbate adsorbed and the equilibrium concentration in the bulk solution, qm, the maximum adsorbed amount, and K is the adsorption equilibrium constant. Carboxylic acids having plural carboxyl groups had much higher affinity to the surface and were adsorbed in both reversible and irreversible modes. The adsorption isotherms for the carboxylic acids having plural carboxyl groups could be expressed by a modified Langmuir-type adsorption isotherm, i.e., Q=q(irrev)+Kq(rev)C/(1+KC), where q(irrev) and q(rev) are, respectively, the maximum amounts adsorbed irreversibly and reversibly. The K and q(irrev) values increased with an increase in the number of carboxyl groups except for isophthalic acid and terephthalic acid. On the basis of the pH dependencies of K, qm, q(irrev), and q(rev) as well as the surface properties of the stainless steel, both reversible and irreversible adsorptions were considered to occur through the electrostatic interaction between negatively charged carboxyl groups and the positively charged sites on the surface. The dependency of the q(irrev) value on ionic strength was discussed on the basis of the differences in their adsorbed state with the interaction forces to the surface and repulsive forces among the adsorbed molecules. The adsorption of amine components was quite weak. The RA-IR and molecular dynamics calculation were done to investigate the adsorption states of phthalic acid, trimellitic acid, and mellitic acid.     

Molecular orientation of rigid‐rod polyimide films characterized by polarized attenuated total reflection/fourier transform infrared spectroscopy

The variations in the molecular orientation of uniaxially drawn rigid‐rod polyimide films were systematically characterized in all three dimensions with polarized attenuated total reflection/Fourier transform infrared spectroscopy. The second‐order orientation coefficients were directly deduced from the anisotropy in IR absorptions of particular bands. With the draw ratio increasing, the state of the molecular orientation changed from being nearly planar to completely uniaxial via biaxial orientation, and the degree of orientation was much larger than that of a semirigid polyimide having an ether linkage at the same draw ratio, which originated from the rigid‐rod structure. In addition, the imide planes were rotationally oriented to the out‐of‐plane direction of the film geometry. Furthermore, the relationship between the molecular chain orientation and the in‐plane birefringence in the biaxial orientation state was examined. The intrinsic birefringence was estimated from biaxial orientation films to be 0.33 at a wavelength of 1307 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 418–428, 2003