Development of chiral pincer palladium complexes bearing a pyrroloimidazolone unit. Catalytic use for asymmetric Michael addition

Novel pincer palladium complexes having chiral hexahydro-1H-pyrrolo[1,2-c]imidazolone groups were designed and prepared. Catalytic asymmetric Michael addition of isopropyl 2-cyanopropionate to ethyl vinyl ketone was catalyzed by the chiral pincer palladium complex to give isopropyl 2-cyano-2-methyl-5-oxoheptanoate with high enantioselectivity (up to 83% ee). [structure: see text]     

Synthesis and characterization of organometallic conjugated polymers containing tricarbonyl(arene)chromium unit and platinum

Novel organometallic conjugated polymer containing (η⁶-arene)Cr(CO)₃ and platinum in the main chain was synthesized by dehydrohalogenation coupling reaction of (η⁶-1,4-diethynylbenzene)tricarbonylchromium with trans-(PBu₃)₂PtCl₂. The polymer was soluble in common organic solvents and has the number-average molecular weight of 31,000 by GPC analysis. The polymer exhibited an absorption peak derived from π-π^∗ interaction at 358 nm in the UV-Vis spectrum, which showed a red shift of approximately 90 nm compared to that of the model compound. The photochemical ligand exchange reaction of the polymer was also investigated.     

Simultaneous determination of radionuclides separable into natural decay series by use of time-interval analysis

A delayed coincidence method, time-interval analysis (TIA), has been applied to successive – decay events on the millisecond time-scale. Such decay events are part of the ²²⁰Rn²¹⁶Po (T_1/2 145 ms) (Th-series) and ²¹⁹Rn²¹⁵Po (T_1/2 1.78 ms) (Ac-series). By using TIA in addition to measurement of ²²⁶Ra (U-series) from -spectrometry by liquid scintillation counting (LSC), two natural decay series could be identified and separated. The TIA detection efficiency was improved by using the pulse-shape discrimination technique (PSD) to reject -pulses, by solvent extraction of Ra combined with simple chemical separation, and by purging the scintillation solution with dry N₂ gas. The U- and Th-series together with the Ac-series were determined, respectively, from alpha spectra and TIA carried out immediately after Ra-extraction. Using the ²²¹Fr²¹⁷At (T_1/2 32.3 ms) decay process as a tracer, overall yields were estimated from application of TIA to the ²²⁵Ra (Np-decay series) at the time of maximum growth. The present method has proven useful for simultaneous determination of three radioactive decay series in environmental samples.     

Novel spirocyclic trichothecanes, spirotenuipesine A and B, isolated from entomopathogenic fungus, Paecilomyces tenuipes

Entomopathogenic fungi forming fruiting bodies have been employed as tonics and antitussives from ancient times. Paecilomyces tenuipes, which is also called Isaria japonica, is a very popular entomopathogenic fungus and is often considered a health food in northeast Asian countries such as China, Korea, and Japan. We cultivated the fruiting bodies of Paecilomyces tenuipes. Among the large-scale cultivations, fruiting body grown in barley grain contained two novel spirocyclic trichothecane derivatives, spirotenuipesine A (1) and B (2), and known trichothecane mycotoxins. Compounds 1 and 2 showed potent activity in neurotrophic factor biosynthesis in glial cells. The isolation of these compounds indicated that P. tenuipes is a promising source for producing various biologically active substances including trichothecanes. It is noteworthy that trichothecane mycotoxins are present in Paecilomyces tenuipes, which is typically used in medicinal health food.     

Modern microscopy methods for the structural study of porous materials

This article describes a number of important recent microscopy tools and their application in particular to the study of porous inorganic materials. The authors believe that these new techniques are on the threshold of delivering enormous new power in the chemist's arsenal for understanding new and complex behaviour in multi-component, hierarchical or composite materials. In particular we consider the contribution of electron crystallography, three-dimensional electron tomography, ultra-high resolution scanning electron microscopy as well as the combined application of high-resolution electron microscopy and atomic force microscopy to the study of surfaces and crystal growth. Much of this work has taken on a particular significance owing to the ground breaking work of scientists at Mobil and in Japan 10 years ago in the successful synthesis of materials with porosity on many length scales achieved through the cooperative self-assembly between inorganic and organic phases. This resulted in a series of materials known as M41S of which MCM-41 and MCM-48 were two of the first and most important structures to be synthesised. This has led to a wealth of new porous structures with order over many length scales and has presented new problems in characterisation. Microscopy methods properly executed are particularly important in the study of this new class of material.     

Fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes containing ethyleneglycol units

The fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes having mono-, di-, tri-, and tetra(ethyleneglycol) units were examined. The mono(ethylenglycol) derivative was solid at room temperature, whereas the di-, tri-, and tetra(ethylenglycol) derivatives were oily. The monoethyleneglycol derivative showed weak aggregation-induced emission enhancement with fluorescence maximum at 649 nm, which comes from J-aggregates. The fluorescence of oily di-, tri-, and tetra(ethyleneglycol) derivatives in neat form was very weak. No aggregation-induced emission enhancement was observed for the oily derivatives.     

Reaction of 2,3-diaminomaleonitrile with diones

2,3-Diaminomaleonitrile (DAMN) was allowed to react with 2,6-heptanedione to produce (2Z)-2-amino-3-[(1E)-3-methylcyclohex-2-enylideneamino]but-2-enedinitrile and (2Z)-2-amino-3-[(1Z)-3-methylcyclohex-2-enylideneamino]but-2-enedinitrile. The reaction of DAMN with 2,7-octanedione yielded trans-5,8a-dimethyl-1,5a,6,7,8,8a-hexahydrocyclopenta[e]-1,4-diazepine-2,3-dicarbonitrile. DAMN reacted with 2,8-nonanedione to afford trans- and cis-5,9a-dimethyl-5a,6,7,8,9,9a-hexahydro-1H-benzo[e]-1,4-diazepine-2,3-dicarbonitrile. These compounds were characterized by X-ray crystallography, NMR spectroscopy, and DFT calculations.     

Brönsted acid ionic liquid-catalyzed direct benzylation, allylation and propargylation of 1,3-dicarbonyl compounds with alcohols as well as one-pot synthesis of 4H-chromenes

Recyclable ionic Brönsted acid was prepared in nearly quantitative yield by reacting 1-butylimidazole with an equimolar amount of 1,3-propanesultone, followed by treatment with an equimolar amount of trifluoromethanesulfonic acid. The ionic Brönsted acid-catalyzed direct benzylation, allylation and propargylation of 1,3-dicarbonyl compounds with various alcohols in ionic liquid [N-ethyl-N-methyl imidazolium trifluoromethanesulfonate (EMIOTf)], at 100 °C for 3 h proceeded smoothly to give the corresponding products in good to excellent yields without the use of any hazardous or volatile solvents and without any by-product such as salts. Furthermore, tandem benzylation-cyclization-dehydration of 1,3-dicarbonyl compounds to give functionalized 4H-chromenes was also achieved in this catalytic reaction.