Intrazeolite photooxygenation of chiral alkenes. Control of facial selectivity by confinement and cation-π interactions

Depending on the nature of the substituents on the stereogenic carbon atom, the ene reaction of singlet oxygen with several chiral alkenes by confinement within thionin-supported zeolite NaY, may exhibit significant changes on facial selectivity by comparison to their photooxygenation reaction in solution. It is proposed that, apart from the conformational consequences as a result of the alkene confinement within the zeolite cavities, a synergism between Na⁺-π interactions and singlet oxygen-Na⁺ interactions plays a significant role in the transition states of ene hydroperoxidation. Within NaY, the diastereoselectivity may significantly depend on the site selectivity, as probed through specific deuterium labelling of trisubstituted alkenes bearing a gem-dimethyl group. In certain cases, a remote stereogenic centre relative to the reacting double bond may induce enhanced diastereoselection and regioselectivity.     

Synthesis of exact comb polybutadienes with two and three branches

Two methodologies, based on living star polymers and anionic polymerization high vacuum techniques, were used for the synthesis of exact comb polybutadienes (PBds) with two (C‐2 or H‐type) and three identical branches (symmetric, sC‐3, H‐type with an extra identical branch at the middle of the connector and asymmetric, aC‐3, H‐type with the extra identical branch at any other position along the connector). The first methodology involves (a) the selective replacement of the two chlorines of 4‐(dichloromethylsilyl)diphenylethylene (DCMSDPE, key molecule) with 3‐arm star PBds, by titration with identical (C‐2, sC‐3) or different (aC‐3) living 3‐arm star PBds, (b) the addition of s‐BuLi to the double bond of DPE, and (c) the polymerization of butadiene from the newly created anionic site (sC‐3, aC‐3).The second methodology involves the reaction of living stars with dichlorodimethylsilane (C‐2) or the selective replacement of the three chlorines of trichloromethylsilane with star and linear chains (sC‐3, aC‐3). Intermediate and final products were characterized via size exclusion chromatography, low angle laser light scattering and ¹H‐NMR. The first methodology does not require fractionation, but in contrast to the second methodology, cannot afford polymers with branches of identical molecular weight. Both methods are general and can be extended to combs with two or three different branches at controllable positions along the backbone. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2597–2607, 2009     

Synthesis and characterization of amphiphilic cationic symmetrical ABCBA pentablock terpolymer networks: Effect of hydrophobic content

Group transfer polymerization was employed for the preparation of six amphiphilic terpolymer networks comprising the hydrophilic, pH‐responsive 2‐(dimethylamino)ethyl methacrylate (DMAEMA), the neutral hydrophilic methoxy hexa(ethylene glycol) methacrylate (HEGMA), and the hydrophobic n‐butyl methacrylate (BuMA). 1,4‐Bis(methoxytrimethylsiloxymethylene)cyclohexane was used as a bifunctional initiator, whereas ethylene glycol dimethacrylate served as the crosslinker to interconnect the linear terpolymer precursors to three‐dimensional terpolymer network structures. Five of the terpolymer networks were model, with linear chains between crosslinks of precise length. Four of the five model networks were based on ABCBA pentablock terpolymers with theoretical structure DMAEMA₅‐b‐BuMA_n/2‐b‐HEGMA₁₀‐b‐BuMA_n/2‐b‐DMAEMA₅ with n values equal to 5, 10, 20, and 30. The model network based on the equimolar statistical terpolymer and the nonmodel randomly crosslinked terpolymer network were also prepared. The molecular weights and compositions of the linear pentablock terpolymer precursors to the networks were found to be close to the theoretically expected, while the network sol fractions were found to be relatively low. The degrees of swelling of the networks in water were found to decrease with increasing the hydrophobic content, whereas those in THF exhibited the opposite trend. Small‐angle neutron scattering in deuterium oxide indicated structural organization in the most hydrophobic pentablock terpolymer networks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4420–4432, 2008     

Anionic homo‐ and copolymerization of styrenic triple‐tailed polybutadiene macromonomers

A number of well‐defined complex macromolecular architectures have been synthesized using an efficient macromonomer technique. Styrenic triple‐tailed polybutadiene (PBd) macromonomers (sTMMB), synthesized by selective reaction (titration) of living PBd tails with the SiCl groups of 2‐(dichloromethylsilyl)ethylchloromethylsilyl‐4‐styrene (TCDSS), were polymerized in situ without isolation of sTMMB with s‐BuLi, using high vacuum techniques. Taking advantage of the living character of the anionic polymerization of sTMMB, the following complex macromolecular architectures were prepared: PBd‐g‐(PBd)₃ (triple‐combs), PS‐g‐(PBd)₃ (triple‐grafts), [PBd‐g‐(PBd)₃]₃ (3‐arm triple‐comb stars), and triple molecular brushes (tmbPBd) or triple polymacromonomers (tPMMB). Characterization carried out by size exclusion chromatography (SEC), equipped with refractive index and light scattering detectors, indicated that the synthesized novel architectures have a high degree of molecular and compositional homogeneity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3513–3523, 2007     

Modeling of Electrical Crosstalk in OEIC Modules

A complete set of tools for the calculation of electrical crosstalk in optoelectronic integrated circuits is presented. Typical chip architecture has been analyzed and relative results are obtained. The model can be easily applied to several wire-bonded and flip-chip OEICs. Design guidelines are presented and discussed.     

Byzantine wall paintings from Kastoria, northern Greece: spectroscopic study of pigments and efflorescing salts

This study concerns the investigation of pigments and efflorescence phenomena on the wall paintings of Kastoria, a rural, non-metropolitan Byzantine town. A large number of representative samples were collected from the murals of three churches, dated to post-Byzantine era (14th-17th c. AD). The identified pigments for the red colour were hematite (Fe2O3), cinnabar (HgS) and minium (Pb3O4), while brown and yellow colours were attributed to mixtures of ochres (Fe-oxides and hydroxides) and lime. The utilization of admixtures of iron, lead and mercury compounds was also attested in order to render specific tones on the painted surfaces. Black and dark blue hues were prepared using black carbon and Mn in some cases. Grey colours were assigned to a mixture of black carbon and lime. Green colour is rather attributed to admixtures of Fe-rich minerals and lime and not to the commonly used green earths. Baryte (BaSO4) was also evidenced as a filler or extender. Phosphorous was detected and connected to proteinaceous material and Mo and Sb were traced which are probably affiliated to Fe-oxides. Regarding efflorescing salts, the determined compounds are: calcite, dolomite, gypsum, halite, nitratine, natron and mirabilite, all of which are related to temperature and humidity changes and moisture fluctuations inside the wall paintings.     

Isoflavonoid Profiling and Estrogen-Like Activity of Four Genista Species from the Greek Flora

As part of our ongoing research on phytoestrogens, we investigated the phytochemical profile and estrogen-like activities of eight extracts from the aerial parts of four Genista species of Greek flora using estrogen-responsive cell lines. Ethyl acetate and methanolic extracts of G. acanthoclada, G. depressa, G. hassertiana, and G. millii were obtained with accelerated solvent extraction and their phytochemical profiles were compared using ultra-high-performance liquid chromatography-high-resolution mass spectrometry (uHPLC-HRMS). Fourteen isoflavonoids, previously isolated from G. halacsyi, were used as reference standards for their identification in the extracts. Thirteen isoflavonoids were detected in both extracts of G. acanthoclada and G. hassertiana, while fewer and far fewer were detected in G. millii and G. depressa, respectively. The ethyl acetate extracts of G. hassertiana and G. acanthoclada displayed 2.45- and 1.79-fold higher, respectively, estrogen-like agonist activity in Ishikawa cells compared to MCF-7 cells at pharmacologically relevant concentrations. Both these extracts, but not that of G. depressa, contained mono- and di-O-β-d-glucosides of genistein as well as the aglycone, all three of which are known to display full estrogen-like activity at lower-than-micromolar concentrations. The possibility of using preparations rich in G. hassertiana and/or G. acanthoclada extracts as a potentially safer substitute for low-dose vaginal estrogen for menopausal symptoms is discussed.     

Fused dihydrofurans from the one-pot,three-component reaction of 1,3-cyclohexanedione,iodobenzene diacetate and alkenes

The one-pot, three-component reactions of substituted 1,3-cyclohexanediones, iodobenzene diacetate and alkenes, under photochemical activation, yields fused dihydrofuran derivatives in good yield via the in situ formation of iodonium ylides.     

Thermal,mineralogical and spectroscopic study of plasters from three post-Byzantine churches from Kastoria (northern Greece)

Several plaster samples were collected from the wall paintings of post-Byzantine monuments from Kastoria town, northern Greece. They were analysed mainly by simultaneous thermal analysis (TG-DTG/DTA) and X-ray diffraction and supplementary by electron microscope (ESEM-EDX) and Raman spectroscopy. Whitish and dark plaster layers were evident in most cases. Calcite, micas, and quartz were the dominant minerals, while dolomite, gypsum, and feldspar were detected as minor phases in most of the samples. Hydromagnesite and chlinochlore were also determined in a few samples. The utilisation of the results for chronological purposes (i.e. for assignment of different painting periods) was also suggested and the presence of dolomite and hydromagnesite could be characteristic for the provenance of the raw material. Gypsum was regarded mainly as a weathering product due to sulfation process, and secondly as a binding material of the plaster. The thermoanalytical results are in good agreement with the mineralogical data. The white plasters are categorized as hydraulic lime mortars, while the dark ones as natural pozzolanic mortars. Calcite and gypsum correlates well with their respective mass losses at certain temperature ranges and their Raman spectra are clearly detected. ESEM-EDX revealed fine calcareous components with aluminolisilicate aggregates and the application of the fresco technique either as a multi-layer or a single-layer plaster. The deterioration caused by salts (gypsum, halite, and nitratine) and micro-organisms was also determined. The detrimental effect of the salt crystallization and dissolution was also confirmed using the so-called Peltier-stage experiment.     

Easy Access to Crystalline Indolines via Hydrogen Bond Transfer

Several indoline derivatives with specific geometries are biologically active and have inhibitor properties. Many indolines are a key part of natural products. Much attention has been focused on the development of synthetic routes for their easy access. Current synthesis depends largely on metal catalysis, iodine reagents, and Oxone. To date, no synthetic route has been established that is metal‐free, reagent‐free, and environmentally friendly and provides a base for green chemistry. Here, we report the first facile metal‐free and reagent‐free synthesis of indoline derivatives, which could potentially be influential in the design of new biologically active compounds. The synthesis proceeds through intramolecular amination between a urea nucleophile and unactivated alkene. The ring closure occurs in a few hours in the presence of pre‐dried silica gel and gives good yields of indolines products, but in the absence of silica gel, the ring closure occurred overnight with stirring in dry solvent. An electron withdrawing group at the substituted aryl moiety of ureas increases the hydrogen bond donor ability of substrates that mediate the internal proton transfer at the terminal alkene and results in facile amination to give the indoline product with an “in plane” orientation of the carbonyl group and aromatic part of indoline framework. Such orientation in indolines is important for potent biological activities.