Photochemical,Metal-Free Sigmatropic Rearrangement Reactions of Sulfur Ylides

Sigmatropic rearrangement reactions constitute one of the most fundamental reactions of carbenes. While state-of-the-art synthetic methods require the use of expensive precious metal catalysts, the application of visible light for the photolysis of α-aryldiazoacetates is much less investigated and provides an operationally simple entry to carbenes under mild reaction conditions. Herein, we report on blue-light induced sigmatropic rearrangement reactions of sulfur compounds with α-aryldiazoacetates. This process, depending on the substitution pattern of the sulfide, opens up formal insertion reactions of carbenes into S−N, S−C, or C−H bonds.     

Photoinduced Proton‐Transfer Reactions for Mild O‐H Functionalization of Unreactive Alcohols

Hexafluoroisopropanol is typically considered as an unreactive solvent and not as a reagent in organic synthesis. Herein, we report on a mild and efficient photochemical reaction of aryl diazoacetates with hexafluoroisopropanol that enables, under stoichiometric reaction conditions, the synthesis of fluorinated ethers in excellent yield. Mechanistic studies indicate there is a preorganization of hexafluoroisopropanol and the diazoalkane acts as an unreactive hydrogen‐bonding complex. Only after photoexcitation does this complex undergo a protonation‐substitution reaction to the reaction product. Investigations on the applicability of this photochemical transformation show that a broad variety of acidic alcohols can be subjected to this transformation and thus demonstrate the feasibility of this concept for O‐H functionalization reactions (54 examples, up to 98 % yield).     

Application of planning models in the agri-food supply chain: A review

The supply chain of agricultural products has received a great deal of attention lately due to issues related to public health. Something that has become apparent is that in the near future the design and operation of agricultural supply chains will be subject to more stringent regulations and closer monitoring, in particular those for products destined for human consumption (agri-foods). This implies that the traditional supply chain practices may be subject to revision and change. One of the aspects that may be the subject of considerable scrutiny is the planning activities performed along the supply chains of agricultural products. In this paper, we review the main contributions in the field of production and distribution planning for agri-foods based on agricultural crops. We focus particularly on those models that have been successfully implemented. The models are classified according to relevant features, such as the optimization approaches used, the type of crops modeled and the scope of the plans, among many others. Through our analysis of the current state of the research, we diagnose some of the future requirements for modeling the supply chain of agri-foods.     

Binding modes of a dimethyliminopentanone ligand on nickel pre-catalysts toward olefin polymerization

Nickel complexes prepared using a 4-(2,6-diisopropylphenylimino)-3,3-dimethylpentan-2-one ligand framework are shown. The potassium salt of the ligand is obtained by deprotonation with KH in diethyl ether. Potassium 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olate can then be reacted with Ni(PMe₃)₂(η¹-CH₂Ph)Cl to yield 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ¹O](η¹-CH₂Ph)(PMe₃)₂Ni (1). The potassium salt of the ligand can also be reacted with Ni(PMe₃)(η³-CH₂Ph)Cl to yield bis(4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ²N,O](η¹-CH₂Ph)₂Ni₂ (2) or 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ²N,O](η¹-CH₂Ph)(PMe₃)Ni (3), depending on the reaction conditions. The addition of five equivalents of B(C₆F₅)₃ to 1, 2, or 3 yields catalytically active species for the homopolymerization of ethylene. The polymer products are described by a single molecular weight distribution, consistent with the presence of a single active site.     

Automated nucleic acids isolation using paramagnetic microparticles coupled with electrochemical detection

Easy, efficient and low demanding separation of mRNA from biological material is needed to study gene expression and to use in chip technologies. It is common knowledge that each mRNA molecule contains sequence of 25 adenines. This feature can be used for binding mRNA on the surface of the particles coated by thymine chains. The present work reports on suggesting and optimizing of mRNA separation and detection from biological material via paramagnetic microparticles coupled with electrochemical detection. Primarily we optimized cyclic and square wave voltammetric conditions to detect poly(A), which was used as standard to mimic behaviour of mRNA. Under the optimized square wave voltammetric conditions (frequency 280 Hz, accumulation time 200 s, supporting electrolyte and its temperature: acetate buffer 4.6 and 35 °C) we estimated detection limit down to 1 ng of poly(A) per ml. To enhance effectiveness and repeatability of isolation of nucleic acid automated approach for rinsing and hybridizing was proposed. We optimized the whole procedure and experimental conditions. Using automated way of isolation and under optimized conditions the yield of poly(A) (isolated concentration of poly(A)/given concentration of poly(A)*100) was approximately 75%. The suggested and optimized method for poly(A) isolation and detection was utilized for the analysis of brain tissues of patients with traumatic brain injury. The total amount of isolated mRNA varied from 40 to 760 g of mRNA per g of brain tissue. The isolation of mRNA from six samples per run was not longer than 2.5 h. Moreover, we applied the optimized procedure on fully automated pipetting instrument to isolate mRNA. The instrument was successfully tested on the analysis of extracts from roots of maize plants treated with cadmium(II) ions.     

Investigation of heavy metal distributions along 15 m soil profiles using EDXRF,XRD, SEM‐EDX,and ICP‐MS techniques

The research of soil contamination by heavy metal is an important field due to its environmental and health implications. The goal was to study the elemental mobility as a function of depth. For this reason, the distribution of heavy metals (V, Cr, Co, Ni, Cu, Zn, As, Sn, and Pb) was investigated along soil profiles up to a depth of 15 m at 9 sampling sites in the Nilufer industrial district (Bursa, Turkey). Elemental analyses were done with the Epsilon 5 energy dispersive X‐ray fluorescence and inductively coupled plasma mass spectrometry equipment. Particle analysis was performed with a JEOL scanning electron microscope equipped with a Si(Li) X‐ray detector. The crystallographic compositions of oxide compounds in soil samples were identified by a Rigaku X‐ray diffraction instrument. Different parameters such as the soil's chemical (mineralogical structure, pH, and electrical conductivity) and physical properties (the number of blows, the stiffness index, the liquidity index, the plasticity index, and the water content) were analyzed. To assess the mobility of the heavy metals, diffusion (D) and convection coefficients (?) were calculated with the finite difference method. Convection was determined to dominate the studied region. In addition, the mobility coefficient was determined for each metal. High mobilities were determined for Zn and V, moderate mobilities for Cr, Ni, Cu, and As, and low mobilities were determined for Co and Pb. The results revealed that elements had reached depths of up to 15 m, causing irreversible soil contamination that may lead to environmental health issues.     

Adsorption of cadmium and lead onto oxidized nitrogen-doped multiwall carbon nanotubes in aqueous solution: equilibrium and kinetics

Nitrogen-doped multiwall carbon nanotubes (CNx) were chemically oxidized and tested to adsorb cadmium and lead from aqueous solution. Physicochemical characterization of carbon nanotubes included morphological analysis, textural properties, and chemical composition. In addition, the cadmium adsorption capacity of oxidized-CNx was compared with commercially available activated carbon and single wall carbon nanotubes. Carboxylic and nitro groups on the surface of oxidized CNx shifted the point of zero charge from 6.6 to 3.1, enhancing their adsorption capacity for cadmium and lead to 0.083 and 0.139 mmol/g, respectively, at pH 5 and 25 °C. Moreover, oxidized-CNx had higher selectivity for lead when both metal ions were in solution. Kinetic experiments for adsorption of cadmium showed that the equilibrium was reached at about 4 min. Finally, the small size, geometry, and surface chemical composition of oxidized-CNx are the key factors for their higher adsorption capacity than activated carbon.     

Electrophoretic and chromatographic evaluation of transgenic barley expressing a bacterial dihydrodipicolinate synthase

Nutritional quality of human and animal foodstuffs is determined by the content of essential amino acids. Barley is the fourth most important cereal of the world and the second most important cereal grown in the Czech Republic. Cereal grains such as barley contain insufficient levels of some essential amino acids, especially lysine. Dihydrodipicolinate synthase is the key enzyme involved in the regulatory step for lysine biosynthesis. Two constructs pBract214::sTPdapA and pBract214::mdapA containing the dapA gene from Escherichia coli coding for the bacterial dihydrodipicolinate synthase were used for transformation of barley. An Agrobacterium-mediated technique was used for transformation of immature embryos of spring barley cv. Golden Promise. Transgenic barley plants of the T0 and T1 generations were evaluated by PCR, real-time PCR, gel electrophoresis, and Western blot. Amino acid content was analyzed by HPLC after HCl hydrolysis. The lysine content in leaves of the T1 generation plant no. 5/5 was 50% higher than in wild-type plants; the lysine content in seeds of T2 generation plant no. 5/16 was 30% higher than in wild-type seeds of spring barley cv. Golden Promise.     

The application of (Z)-3-aryl-3-haloenoic acids to the synthesis of (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones

Studies directed at the synthesis of (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones from (Z)-3-aryl-3-haloenoic acids are described. The successful strategy relies on the preparation of (Z)-3-aryl-3-haloenoic acids from acetophenones through the corresponding (Z)-3-aryl-3-haloenals and the conversion of the (Z)-3-aryl-3-haloenoic acids to (Z)-5-benzylidene-4-aryl-5H-furan-2-ones. The furanones were subsequently treated with primary amines and dehydrated to the corresponding (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones.