Montmorillonite-K10 Catalyzed Addition OF Trimethylsilylcyanide (TMSCN) to Aldehydes.

Addition of trimethylsilyl cyanide (TMSCN) to aldehydes was catalyzed by Montmorillonite-K10, with subsequent reduction to β-aminoalcohol.     

Synthesis of Tuberine

Tuberine, has been synthesized by syn sulfoxide elimination to introduce the enamide function.     

Synthetic and natural silica‐aluminates as inorganic acidic catalysts in ring opening polymerization of cyclosiloxanes

Ring opening polymerization (ROP) of hexamethylcyclotrisiloxane (D₃) and octamethylcyclotetrasiloxane (D₄) was promoted by acid‐treated synthetic and natural silica‐aluminates. Silica‐alumina (1:3 Si/Al molar ratio) was obtained using a simple and economic route from precipitation of aluminum sulfate solutions. The material was treated in an acidic medium to improve the content of acid sites and successfully tested as inorganic acidic catalyst for ROP of D₃ or D₄ cyclosiloxanes. Natural bentonite was treated and used in a similar manner. Once the ROP reaction completed, the catalyst was easily removed and it was found that the recovered synthetic silica‐alumina was active in a second ROP reaction. The effect of the concentration and type of catalyst in respect to the molecular weight and polydispersity of polydimethylsiloxanes was analyzed: increasing the amount of silica‐alumina in ROP of D₄ from 0.05 to 0.1 g decreased the average molecular weight (M_n = 13–1.8 kDa) associated with an increase in the polydispersity (2.95 vs. 1.81). Analogous results were found with bentonite. These values suggest that an increase in the catalyst concentration led to a lower M_n, with a more homogeneous molecular chain dimension. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of (R)-tembamide and (R)-aegeline via asymmetric transfer hydrogenation in water

The synthesis of (R)-tembamide and (R)-aegeline via asymmetric transfer hydrogenation involving enantioenriched monosulfonamide–RhCp¹ complex in aqueous sodium formate as hydride donor is described.     

Design and operation issues using NLP superstructure modeling

Till present, models that determined batch plants configurations in the chemical process industry resorted to models with binary variables to represent the different admissible options. This approach allowed representing the problem in a simple way while considering a significant number of alternatives. Nevertheless, the non-convexity that arises when dealing with detailed models for representing the involved units operation prevents its correct resolution or has a low performance. This work presents a representation of the problem through a superstructure that takes explicitly into account all the alternatives without resorting to binary variables. By using extremely simple modeling, it is possible to manage an appropriate number of options for this type of problems by means of a non-linear programming (NLP) model. Moreover, it is possible to consider duplication in series of production stages, which is an alternative that has not been used till now. This approach is posed for the case of a fermentors network. The solution is reached with very low requirements as regards employed computer time and without the aforementioned difficulties.     

On the product of distributions with coincident point singularities

In this paper we generalize the result obtained by Gonzáles Domínguez, Scarfiello and Fisher (A. Gonzáles Domínguez and R. Scarfiello, Rev. Un. Mat. Argentina, Volumen de Homenaje a Beppo Levi (1956) 58–67; B. Fisher, Proc. Cambridge Philos. Soc. 72 (1972) 201–204). This result can be used in quantum field theory for the evaluation of products of propagators of the fields. With this new result we obtain the product . As a physical example, we evaluate the selfenergy Green function of a massless scalar field.     

Complexes of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (4,13-diaza-18-crown-6) with 2,5-pyridinedicarboxylic and 2,2′-dithiosalicylic acids

A 1:2:2 complex of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane with 2,5-pyridinedicarboxylic acid and water (1) and its 1:1:1.75 complex with 2,2-dithiosalicylic acid and water (2) have been obtained and characterized by x-ray diffraction. C₂₆H₄₀N₄O₁₄ (1), triclinic, , a = 9.574(1) Å, b = 9.632(1) Å, c = 9.723(1) Å, = 112.70(1)°, = 91.07(1)°, = 115.45(1)°, V = 728.35(13) ų, Z = 1. C₂₆H_39.5N₂O_9.75S₂ (2), M = 600.22, triclinic, , a = 10.492(1) Å, b = 10.945(1) Å, c = 14.535(2) Å, = 102.74(1)°, = 109.08(1)°, = 90.68(1)°, V = 1532.2(3) ų, Z = 2. In complex 1, both N-atoms of the macrocyclic ring are protonated. The following types of H-bonding have been found: (1) between protonated aza groups of the macrocycle and ionized carboxylic groups; (2) between the protonated aza groups and N-atoms of the pyridine nuclei (D–A distance slightly exceeds 3 Å); (3) between water molecules and C=O groups of the non-ionized carboxylic groups; and (4) between the nonionized and ionized groups of the carboxylic acid. The above interactions give rise to the formation of a developed supramolecular network in the crystals of 1. In complex 2, despite the presence of several types of hydrogen bonds involving the aza crown, 2,2-dithiosalicylic acid and water, the aromatic anions are H-bound only to the two other components, and not to each other. The H-bonds found in complex 2 are between (1) one of the protonated aza groups and water, (2) protonated aza groups and O-atoms of the ionized carboxylic groups, (3) water molecule and carboxylic O-atom, (4) water molecule and sulfur atom, and (5) water molecule and O-atom of diaza-18-crown-6.