The Synthesis of Linearly Annelated Polycyclic Ketones by Friedel-Crafts Rearrangements of Their Angular Isomers

Derivatives of 5H-dibenzo[a, d]cycloheptene carrying an alkylamine side chain at position 5 serve as useful drugs in the chemotherapy of mental diseases.^1–2 During a study of the effect of annelation on the activity of these psychopharmacological agents of the amitryptyline type, it was deemed necessary to synthesize the linear 13,14-dihydro-6H-cyclohepta-[1,2-b:4,5-b']dinaphthalen-6-one (I). The method of approach was the general synthesis of the polycyclic skeleton of amitryptyline, in which the seven-membered ring is constructed by a Friedel-Crafts (F - C) intramolecular acylation.^3–4 Ketone I, however, contains two 2,3-disubstituted naphthalene moieties condensed to the central seven-membered ring.     

Polymer entanglement loss in extensional flow: Evidence from electrospun short nanofibers

High strain rate extensional flow of a semidilute polymer solution can result in fragmentation caused by polymer entanglement loss, evidenced by appearance of short nanofibers during electrospinning. The typically desired outcome of electrospinning is long continuous fibers or beads, but, under certain material and process conditions, short nanofibers can be obtained, a morphology that has scarcely been studied. Here we study the conditions that lead to the creation of short nanofibers, and find a distinct parametric space in which they are likely to appear, requiring a combination of low entanglement of the polymer chains and high strain rate of the electrospinning jet. Measurements of the length and diameter of short nanofibers, electrospun from PMMA dissolved in a blend of CHCl₃ and DMF, confirm the theoretical prediction that the fragmentation of the jet into short fibers is brought about by elastic stretching and loss of entanglement of the polymer network. The ability to tune nanofiber length, diameter and nanostructure, by modifying variables such as the molar mass, concentration, solvent quality, electric field intensity, and flow rate, can be exploited for improving their mechanical and thermodynamic properties, leading to novel applications in engineering and life sciences. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1377–1391     

Simulated moving bed technology to improve the yield of the biotechnological production of lactobionic acid and sorbitol

This work presents an analysis on the suitability of the Simulated Moving Bed (and pseudo-SMB) technology on separating the mixture obtained from the lactose oxidation catalyzed by glucose-fructose oxidoreductase and glucono-α-lactonase enzymes. These enzymes from the Zymomonas mobilis bacteria are able to oxidize lactose in presence of fructose to its respective organic acid—lactobionic acid—and sorbitol. Some alternative arrays of chromatographic systems, as fixed bed column, SMB unit, 4 section pseudo-SMB, have been explored to separate the multi-component mixture, in such way to make possible the product recovery and the recycle of substrates to the enzymatic reactor. This study involved the definition of appropriate operating conditions and the prediction of the performance of the separation units, or arrangement of units, through modeling and simulations tools. To define the proper operating conditions, inequalities from equilibrium theory and the concept of the separation volume analysis have been considered. In this analysis, equilibrium and kinetic parameters for the compounds adsorbing on DOWEX 50W-X4 resin, in K⁺ and Ca⁺² ion-loadings, have been obtained from chromatographic methods (pulse and adsorption-desorption techniques). The enzymatic kinetic of production of lactobionic acid and sorbitol using permeabilized cells of Z. mobilis is shown. The strategy of keeping the highest value of reaction rate by the integration of a chromatographic system proved to be viable when it was found the feasibility to apply the SMB system in cascade.     

Ca4Fe3−xMnxO8−δCl2: A new n=3 Ruddlesden–Popper oxychloride

Solid state solutions of Ca₄Fe_3?xMn_xO_8?δCl₂ (0.92≤x≤1.79 (δ～0.1) single crystals were synthesized in CaCl₂-flux in air. The structure, determined by single-crystal X-ray diffraction, is related to the n=3 Ruddlesden–Popper phase in space group I4/mmm with strong deviations from the ideal structure. Mn and Fe are disordered over two transition metal sites. Due to the positional disordering of the equatorial oxygen atoms in the MO₆ octahedra in Ca₄Fe_3?xMn_xO_8?δCl₂ both tilting (～9°) along the c-axis and rotation (～10.5°) within the ab-plane are observed. All the Fe ions are trivalent, as confirmed by ⁵⁷Fe Mössbauer spectroscopy and X-ray absorption near edge spectroscopy (XAS), while the formal valence state of Mn varies from very close to 4+ in the x=0.92 to mix-valent 3+/4+ in the x=1.79 member, as indicated by XAS. Magnetic investigations evidence short-range antiferromagnetic ordering already at room temperature and spin-glass behavior at low temperature due to the structural disordering of Mn/Fe.     

Coordination and hydrogen‐bonding assemblies in hybrid reaction products between 5,10,15,20‐tetra‐4‐pyridylporphyrin and dysprosium trinitrate hexahydrate

Reactions of the title free‐base porphyrin compound (TPyP) with dysprosium trinitrate hexahydrate in different crystallization environments yielded two solid products, viz. [μ‐5,15‐bis(pyridin‐1‐ium‐4‐yl)‐10,20‐di‐4‐pyridylporphyrin]bis[aquatetranitratodysprosium(III)] benzene solvate, [Dy₂(NO₃)₈(C₄₀H₂₈N₈)(H₂O)₂]·C₆H₆, (I), and 5,10,15,20‐tetrakis(pyridin‐1‐ium‐4‐yl)porphyrin pentaaquadinitratodysprosate(III) pentanitrate diethanol solvate dihydrate, (C₄₀H₃₀N₈)[Dy(NO₃)₂(H₂O)₅](NO₃)₅·2C₂H₆O·2H₂O, (II). Compound (I) represents a 2:1 metal–porphyrin coordinated complex, which lies across a centre of inversion. Two trans‐related pyridyl groups are involved in Dy coordination. The two other pyridyl substituents are protonated and involved in intermolecular hydrogen bonding along with the metal‐coordinated water and nitrate ligands. Compound (II) represents an extended hydrogen‐bonded assembly between the tetrakis(pyridin‐1‐ium‐4‐yl)porphyrin tetracation, the [Dy(NO₃)₂(H₂O)₅]⁺ cation and the free nitrate ions, as well as the ethanol and water solvent molecules. This report provides the first structural characterization of the exocyclic dysprosium complex with tetrapyridylporphyrin. It also demonstrates that charge balance can be readily achieved by protonation of the peripheral pyridyl functions, which then enhances their capacity in hydrogen bonding as H‐atom donors rather than H‐atom acceptors.     

Synthesis and Properties of Mononuclear Group 10 Alkoxy‐Biscarbene Complexes

New Pd ‐ and Pt‐biscarbenes : The synthesis by the stoichiometric transmetalation reactions from Fischer alkoxy‐chromium(0) carbene complexes of stable mononuclear (palladium and platinum) alkoxy‐biscarbene complexes is reported. The structure, bonding situation, and the electronic and redox properties of these complexes are studied by a combination of experimental and computational (DFT) methods.

     

Synthesis,structure, electrochemistry,and Mössbauer effect studies of (ring)Fe complexes (ring = Cp,Cp1, and C6H7). Photochemical replacement of benzene in the cyclohexadienyl complex [(η5-C6H7)Fe(η-C6H6)]+

Visible light irradiation of cation [(η⁵-C₆H₇)Fe(η-C₆H₆)]⁺ (1⁺) in acetonitrile results in substitution of the benzene ligand giving the labile acetonitrile derivative [(η⁵-C₆H₇)Fe(MeCN)₃]⁺ (2a⁺). The stable isonitrile and phosphite complexes [(η⁵-C₆H₇)FeL₃]⁺ [L = ^tBuNC (2b⁺), P(OMe)₃ (2c⁺), P(OEt)₃ (2d⁺)] were obtained by reaction of 1 with L in MeCN. The structures of 2cPF₆, [CpFe(η-C₆H₆)]PF₆ (3PF₆), and Cp¹Fe(η-C₆H₆)]PF₆ (4PF₆) were determined by X-ray diffraction.The redox activity of the cyclohexadienyl complexes 1⁺, 2b⁺?2d⁺ has been investigated by electrochemical techniques and compared with that of the related cyclopentadienyl complexes 3⁺ and 4⁺. DFT calculations of the redox potentials and the respective geometrical changes were performed.Variable temperature Mössbauer (ME) spectroscopy has elucidated the relationship between structure and formal oxidation state of the iron atom in these complexes. In the case of 3⁺ an unexpected pair of crystallographic changes has been observed and interpreted in terms of both a second and first order phase transition. The mean-square-amplitude-of-vibration of the metal atom has been compared between the ME and X-ray data. ME measurements in a magnetic field have shown that in 4⁺ the quadrupole splitting is positive as it is in ferrocene.     

Determination of oleic acid in sunflower seeds by infrared spectroscopy and multivariate calibration method

A method for the determination of oleic acid in sunflower seeds is proposed. One hundred samples of sunflower seeds were analyzed by near-infrared diffuse reflectance spectroscopy (NIRDRS). The direct measures were realized in ground and sifted seeds. The PLS multivariate calibration model was obtained using first derivate absorbance values as response matrix, while the oleic acid concentration matrix was obtained analyzing the seed samples by gas chromatography with a flame ionization detector (GC-FID). The NIRDRS-PLS model was validated externally using unknown samples of sunflower seeds. The accuracy and precision of the method was evaluated using GC as reference method. The following figures of merit (FOM) were obtained: LOD = 3.4% (w/w); LOQ = 11.3% (w/w); SEN = 8 × 10⁻⁵; SEL = 0.15; analytical sensibility (γ) = 1.5 and linear range (LR) = 18.1-89.2% (w/w). This method is useful for the fast determination of oleic acid in sunflower seeds and for quality control of raw materials.