Synthesis of 1,2-disubstitued benzimidazoles using SiO2/ZnCl2

A general and easy method for the synthesis of several 1,2-disubstituted benzimidazoles using SiO₂/ZnCl₂ and solvent-free conditions is described. This efficient and improved method furnishes selectively and in good yields the corresponding 1,2-bis(organyl)-benzimidazoles starting from o-phenylenediamine and aromatic or aliphatic aldehydes. The catalytic system was re-used up three times and the use of focused microwaves accelerates the reaction.     

Mathematical modelling of NABD release from endoluminal gel paved stent

Coronary restenosis consists of the partial/total re-occlusion of the artery lumen following percutaneous transluminal angioplasty (PTCA). In order to match this pathology, PTCA is followed by the implantation of rigid scaffolds (stent or coated stent) aimed to contrast the most important mechanical (coronary wall elastic recoil and late remodelling) and biological (smooth muscle cells iper-proliferation) factors leading to restenosis. In the light of the clinical problems recently arisen about the use of traditional coated stents, this paper proposes a theoretical study to comprehend the release kinetics of novel anti-proliferative drugs, i.e. nucleic acid based drugs (NABD), complexed with the proper delivery agent (DA). The release of NABD-DA is supposed to occur from a double gel layer adhering to coronary wall and embedding the stent. The proposed mathematical model assumes that diffusion, convection and cellular internalisation/metabolism are the leading mechanisms ruling drug spreading in the coronary wall. In addition, stent void fraction, positioning (totally embedded or totally out of the coronary wall) and continuous or discontinuous character of the gel layer are other three important model parameters. In order to generalise the results, stent geometry is idealised as a series of not connected, equally spaced, rings positioned in the stented zone. In correspondence of stent strut, drug transport cannot occur. The most important outcomes of this study are that, in the usual void fraction range (0.7-0.9), stent presence does not sensibly affect NABD-DA release kinetics. In addition, whereas stent positioning in the continuous gel configuration (totally embedded or totally out of coronary wall) is not very important, in the discontinuous case, it becomes relevant. Finally, this study evidences that a proper mixture of NABD complexed with different (in dimensions and kind) DA can ensure an almost constant NABD coronary concentration for several months, as requested by clinical observations.     

A centrosymmetric polymorph of chloridotris(triphenylphosphine‐κP)copper(I) at 150 K

This study characterizes a new polymorph of the title compound, [CuCl(C₁₈H₁₅P)₃], and analyses the influence of the extensive network of weak hydrogen‐bonding interactions in the generation of this different crystal structure. The compound crystallizes in the centrosymmetric space group C2/c with two crystallographically independent molecules per asymmetric unit, in contrast with the previously determined polymorph which crystallizes in the noncentrosymmetric space group P3 with three crystallographically independent molecules in the asymmetric unit, each with crystallographically imposed C3 symmetry [Gill, Mayerle, Welcker, Lewis, Ucko, Barton, Stowens & Lippard (1976). Inorg. Chem. 15 , 1155–1168]. The geometries of the two molecules of the title compound are very similar, with each having an approximately tetrahedral coordination around the central Cu atom and approximate C_s molecular symmetry. The molecules pack in chains parallel to the crystallographic b axis, connected by C—H...Cl and C—H...π(phenyl) hydrogen bonds.     

Solvent-free conjugated addition of thiols to citral using KF/alumina: preparation of 3-thioorganylcitronellals, potential antimicrobial agents

A general, clean and easy method for the conjugated addition of thiols to citral promoted by KF/Al₂O₃ under solvent-free conditions at room temperature or under MW irradiation is described. It was found that the same protocol is applicable to the direct reaction of thiophenol with essential oil of lemon grass (Cymbopogon citratus) to afford directly 3-thiophenylcitronellal, a potential bactericide agent. The method was extended to others electron-poor alkenes with excellent results. The catalytic system can be reused up to three times without previous treatment with comparable activity.     

Synthesis of ketene phenyl- and butyltelluroacetals by a Horner-Wittig route

New and efficient methods were developed to prepare ketene organyltelluroacetals in moderate to excellent yields. This was accomplished by reaction of phenyl- or butyltelluromethylphosphonates with phenyl- or butyltellurenyl halides and aldehydes or cyclohexanone, under basic conditions. This Horner-Wittig protocol allows the preparation of several new tri- and tetra-substituted olefins.     

Synthesis of β-Aryl-β-sulfanyl Ketones by a Sequential One-Pot Reaction Using KF/Al2O3 in Glycerol

The title compounds were synthesized by a sequential one-pot reaction of aryl aldehydes, aryl-methyl ketones, and thiols promoted by KF/Al₂O₃. This methodology affords a large number of β-aryl-β-sulfanyl ketone derivatives from aliphatic and aromatic thiols in good yields and is also applicable for solid substrates.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Formation of quasi-regular diffraction patterns in the nonlinear photorefractive Fabry-Perot interferometer

Formation of optical inhomogeneities under self-action of light fields in photorefractive Fabry-Perot interferometers has been experimentally investigated using the samples of Y — and Z-cut lithium niobate. For the interferometer with the Z-cut sample, it is demonstrated that spiral-shaped inhomogeneities and two-dimensional quasi-regular diffraction patterns are formed under the effect of the Gaussian beam about 1mm in diameter and the light field with a homogeneous intensity distribution.     

Transformation of the amplitude profiles of coherent light beams in a nonlinear photorefractive Fabry-Perot interferometer

The transformations of the transverse profiles of laser beams in a nonlinear Fabry-Perot interferometer based on lithium niobate crystals with a surface layer doped with a combination of photorefractive impurities (iron and copper ions) have been experimentally investigated. It is demonstrated that the distribution of transmitted beam intensity significantly changes for a few seconds at milliwatt beam powers.     

KF/Al2O3 and PEG-400 as a recyclable medium for the selective α-selenation of aldehydes and ketones. Preparation of potential antimicrobial agents

2-Phenylseleno aldehydes and ketones were selectively obtained using solid-supported catalyst (KF/Al₂O₃) and PEG-400 as clean, recyclable medium in good to excellent yields. The method was applied in the preparation of highly functionalized 2-phenylseleno citronellal and citronellol, potential bactericide agents. The catalytic system KF/Al₂O₃ and PEG-400 can be re-used for four times without previous treatment.     

Green, catalyst-free thioacetalization of carbonyl compounds using glycerol as recyclable solvent

We describe herein the use of glycerol as an efficient and a recyclable solvent in the thioacetalization of aldehydes and ketones. The catalyst-free reactions proceed easily using glycerol at 90 °C and the corresponding thioacetals were obtained in good to excellent yields. Glycerol was recovered and utilized for further thioacetalization reactions.