Silicon-Containing Condensation Polymers Derived from Long-Chain Fatty Acids

Silicon-containing condensation polymers were prepared starting from difunctional silicon-containing carboxylic acids or diols derived from long-chain fatty acids. Polyesters were synthesized by reaction of diacids containing siloxane linkages with diols, and diols containing siloxane linkages with various diacids. 1,3-Bis (10-carboxydecyl)tetramethyldisiloxane was condensed with various diamines to yield polyamides. 1,3-Bis(11-hydroxyundecyl)tetramethyldisiloxane and 1,3-bis [9(10)-hydroxyoctadecyl]tetramethyldisiloxane were condensed with diisocyanates to yield polyurethanes. Polycarbonates were synthesized by reacting the diols containing siloxane linkages with ethyl chloroformate. Some polybenzimidazols were synthesized by heating the diesters of the silicon-containing carboxylic acids with 3,3′ -diaminobenzidine. Some of the polyurethanes and polybenzimidazoles were thermally stable up to 300°C as indicated by TGA.     

New practical tools for the implementation and use of ultrafast 2D NMR experiments

Ultrafast (UF) 2D NMR is a very promising methodology enabling the acquisition of 2D spectra in a single scan. In the last few years, the analytical performance of UF 2D NMR has been highly increased, consequently maximizing its range of applications. However, its implementation and use by non‐specialists are far from being straightforward, because of the specific acquisition and processing procedures and parameters characterizing UF NMR. To make this methodology implementable and applicable by non‐specialists, we developed a simple routine capable of translating conventional parameters (spectral widths and transmitter frequencies) into specific UF parameters (gradient and chirp pulse parameters). This macro was subsequently implemented in a Web page, which is available for external users. Although the algorithm was designed for two widely used 2D experiments, COSY and HSQC, it can easily be extended to any other pulse sequence. The robustness of this routine was verified successfully on a variety of small molecules. We believe that this tool will eliminate much of the technical difficulties related to UF 2D NMR and will make the technique accessible to a wider audience of organic and analytical chemists. Copyright © 2013 John Wiley & Sons, Ltd.     

Structure elucidation of four prenylindole derivatives from Streptomyces sp. isolated from Ailuropoda melanoleuca feces

Four new prenylindole derivatives, (R)‐6‐(2,3‐dihydroxy‐3‐methylbutyl)indole (1), (R)‐6‐(2,3‐dihydroxy‐3‐methylbutyl)indolin‐2‐one (2), and an unseparated mixture of (Z)‐6‐(4‐hydroxy‐3‐methylbut‐2‐en‐1‐yl)indolin‐2‐one (3a) and (E)‐6‐(4‐hydroxy‐3‐methylbut‐2‐en‐1‐yl)indolin‐2‐one (3b) with a ratio of 3 : 2, were isolated from the culture broth of a streptomycete isolated from Ailuropoda melanoleuca feces. Their structures were elucidated on the basis of 1D and 2D NMR spectroscopic techniques. The absolute configuration of 1 was determined by Mosher's method. Copyright © 2013 John Wiley & Sons, Ltd.     

Correlation of substituted aromatic β‐diketones' characteristic protons chemical shifts with Hammett substituent constants

Influence of dibenzoylmethane's substituents in meta and para positions on chemical shift values of tautomers' characteristic protons was investigated in four solvents with ¹H NMR spectroscopy: acetone‐d₆, benzene‐d₆, CDCl₃ and deuterated dimethyl sulfoxide (DMSO‐d₆). It was proved that the influence of substituents on chemical shifts strongly depends on the kind of the solvent; the greatest changes were observed in benzene‐d₆ and the smallest in CDCl₃. In acetone‐d₆ and DMSO‐d₆, the influence of substituents on chemical shifts is similar and the most regular. It allowed a fair correlation of chemical shifts of para‐substituted dibenzoylmethane derivatives' characteristic protons with Hammett substituent constants in these solvents. In CDCl₃, characteristic protons' chemical shifts were near ¹H NMR spectroscopy measurement error limits, and, therefore, correlation with Hammett substituent constants in this solvent was unsatisfactory. In benzene, although the changes of chemical shifts are the most evident, the changes are also the most irregular, and, therefore, correlation in this solvent failed completely. Results of meta‐substituted derivatives were much more irregular, and their correlation with Hammett substituent constants was poor in all investigated solvents. Copyright © 2013 John Wiley & Sons, Ltd.     

Relationship between Reactivity Ratios and Configuration for Donor—Acceptor Type Copolymers

For binary copolymers from an acrylic monomer (acceptor type, M¹) and an aromatic-substituted monomer (donor type, M₂) a linear relation between log (r₂/r¹) and the probability of “coisotactic” alternating addition is observed. This can be a proof for the influence of monomer polarity on the copolymer configuration.     

Vinyl Polymerization. 436. Effect of Magnetic Field on Uncatalyzed Polymerization

The radical polymerization of vinyl monomers initiated with several kinds of hydrophilic macromolecule was carried out in a magnetic field. The magnetic field promoted the polymerization; the conversion of monomers and the molecular weight of the polymers obtained increased with increasing field strength in the range of 0–0.1 T. The dependence of the composition and tacticity of the mother polymer on the magnitude of the magnetic field was studied. Using graft or block copolymers, which consisted of hard and soft segments, the effect of a magnetic field was further investigated. The degree of hardness and tightness of the hydrophobic areas (reaction areas) formed by the mother polymer in the aqueous solution was found to affect the magnetic field effect on the uncatalyzed polymerization. The overall activation energy obtained in the magnetic field was almost equal to that obtained without a magnetic field.     

Novel Synthesis of some Spiro Heterocycles Derived from 3-Hydroxy-3(2-Oxocyclohexyl)-Indolin-2-One

The reaction of 3-hydroxy-3(2-oxocyclohexyl)indolin-2-one 1 with some active methylene, bidentates, phenylisocyanate, phenylisothiocyanate, carbon disulfide, benzaldehyde, ketoketene S,S-acetal, cyanoketene S,S-acetal, active halo compounds or benzylidenemalononitrile affords a series of new spiro heterocyclic systems.     

Silica Gel Supported Chromium Trioxide: An Efficient Reagent for Oxidative Cleavage of Oximes to Carbonyl Compounds under Mild Condition

A facile, efficient oxidative deblocking of aldoximes and ketoximes to their corresponding aldehydes and ketones have been achieved by using silica gel supported chromium trioxide.