One-pot synthesis of metalated pyridines from two acetylenes, a nitrile, and a titanium(II) alkoxide

Four-component coupling process involving two acetylenes, a nitrile, and a divalent titanium alkoxide reagent, Ti(O-i-Pr)(4)/2i-PrMgCl, directly yielded titanated pyridines in a highly selective manner. The reaction can be classified into four categories: (i) a combination of an internal acetylene, a terminal acetylene, sulfonylnitrile, and the titanium reagent to yield alpha-titanated pyridines, (ii) a combination of an internal acetylene, a (sulfonylamino)acetylene, a nitrile, and the titanium reagent to yield alternative alpha-titanated pyridines, (iii) a combination of an internal acetylene, a (sulfonylamino)acetylene, a nitrile, and the titanium reagent to yield titanated aminopyridines, and (iv) a combination of an acetylenic amide, a terminal acetylene, a nitrile, and the titanium reagent to yield pyridineamides with their side chain titanated. Some of these reactions enabled virtually completely regioselective coupling of two different, unsymmetrical acetylenes and a nitrile to form a single pyridine. Synthetic applications of these reactions have been illustrated in the preparation of optically active pyridines and medicinally useful compounds.     

Synthesis and characteristics of cellulose peroxides of the peracid type having a temperature-responsive function

The synthesis of cellulose peroxides of the peracid type having a temperature-responsive function was studied by using carboxymethyl cellulose (CMC) and acrylic acid (AA)-grafted cellulose, into which the temperature-responsive component, poly(N-isopropylacrylamide) [poly(NIPAAm)], was introduced by a photografting method (λ > 300 nm). Dissolving pulp from softwoods was used as cellulose sample. NIPAAm-grafted CMC samples prepared by photografting with CMC peroxide exhibited a slightly larger temperature-responsive character than the samples prepared by photografting with xanthone photoinitiator, where the grafted CMC samples swelled and shrank in water at 5 °C and 60 °C, respectively. Ungrafted and NIPAAm-grafted CMC samples were subjected to peroxidation with hydrogen peroxide in the presence of methanesulfonic acid. About 90% of the initial amount of peroxide on the ungrafted CMC sample disappeared after thermal decomposition at 50 °C for 60 min. On the other hand, about 50% of the peroxide on the NIPAAm-grafted CMC sample remained stable under the same conditions. Peroxides on AA/NIPAAm-grafted samples, which were prepared by photografting of AA/NIPAAm binary monomers followed by peroxidation with hydrogen peroxide, were more stable towards thermal decomposition than those on NIPAAm-grafted samples.     

Doubly-bridged binuclear complexes of oxomolybdenum(V) and oxotungsten(V) containing sexadentate ligands

Binuclear oxomolybdenum(V) and oxotungsten(V) complexes of the type, [M ₂(O)₂(-X)(-X ¹)], where M=Mo, W;X.X ¹=O, S; L=edta, pdta (n=2-), tpen, tppn (n=2+) (edta^4– =ethylenediaminetetraacetate(4–), pdta=R- orR,S-propylenediaminetetraacetate(4–), tpen=N,N,N ¹,N¹-tetrakis(2-pyridyhnethyl)-ethylenediamine, and tppn=R- orR,S-N,N,N ¹,N¹-tetrakis(2-pyridylmethyl)-propylenediami ne) are reviewed with respect to their preparation, structure, spectroscopic properties, reactivities, and in particular asymmetric distortion around the bicyclo [4.1.1 ] type core and stereoselectivity related to this distortion,Dedicated to Professor Jiaxi Lu on the occasion of his 80th birthday and in recognition of his pioneering contributions.     

Suzuki-Miyaura coupling of diarylmethyl carbonates with arylboronic acids: a new access to triarylmethanes

Suzuki-Miyaura coupling of diarylmethyl carbonates with arylboronic acids proceeded in the presence of [Pd(eta3-C3H5)Cl]2-DPPPent (1,5-bis(diphenylphosphino)pentane) catalyst, yielding a variety of triarylmethanes.     

Improvement of dissolution property of poorly water-soluble drug by novel dry coating method using planetary ball mill

The dissolution property of a poorly water-soluble drug, flurbiprofen (FP), was improved by a novel dry coating method using a planetary ball mill. Several mixtures composed of water-soluble additives (D-mannitol, lactose, and erythritol), light anhydrous silicic acid, and flurbiprofen were prepared. These mixtures and several starches were co-ground in a planetary ball mill, and the surface of the starches was dry coated with the mixtures. The size, appearance, yield, and drug dissolution property of the dry coated preparations were evaluated, and the optimal formulation which improved the dissolution property of poorly water-soluble flurbiprofen was determined. The dissolution rate of FP was increased by dry coating of the surface of starches with microparticulated FP. It was further increased by co-grinding of FP, starch, and a water-soluble additive, or dry coating of the starch surface with microparticulated FP and light anhydrous silicic acid, as a glidant. These co-ground and dry coated preparations could be recovered from the pot of the planetary ball mill readily without adhesion to the inside wall of the pot. These are considered to be novel, industrially applicable methods for improving the dissolution rate of poorly water-soluble drugs.     

Mechanism of enhanced positronium formation in low-temperature polymers

An enhanced positronium (Ps) formation in low-temperature polymers has been widely observed. The additional positronium formation is due to shallow trapped electrons in them. Positron annihilation lifetime spectroscopy was applied to investigate the Ps formation in a series of polymers, such as low-density polyethylene, ethylene-methyl methacrylate copolymers with various methyl methacrylate contents, and pure poly(methyl methacrylate) at low temperature. An analysis of the experimental data based on simple kinetic equations enables one to understand the Ps formation mechanism in polymers during low-temperature positron annihilation experiments as functions of the temperature and elapsed time. Good fittings of the experimental data were obtained. The fitting parameters seemed to show clear physical meanings.     

Correlation factor in tracer diffusion for high tracer concentrations

The meaning of cross terms in the Onsager equation for diffusion in multicomponent systems is clarified based on the Path Probability method of irreversible statistical mechanics. The problems involved in increasing the concentration of tracer atoms in tracer diffusion experiments are discussed. Some comments on the correlation function approach with respect to the present problem are also added.     

Sharp Error Bounds for Asymptotic Expansions of the Distribution Functions for Scale Mixtures

Let Z be a random variable with the distribution function G(x) and let s be a positive random variable independent of Z. The distribution function F(x) of the scale mixture X = sZ is expanded around G(x) and the difference between F(x) and its expansion is evaluated in terms of a quantity depending only on G and the moments of the powers of the variable of the form s/gr - 1, where (> 0) and (= ±1) are parameters indicating the types of expansion. For = -1, the bound is sharp under some extra conditions. Sharp bounds for errors of the approximations of the scale mixture of the standard normal and some gamma distributions are given either by analysis ( = -1) or by numerical computation ( = 1).