Synthesis of peroxide‐curable butyl rubber via suzuki–miyaura coupling of halogenated butyl rubber with 4‐vinylphenylboronic acid

The Suzuki–Miyaura coupling reaction of brominated butyl rubber (BIIR) and/or chlorinated butyl rubber with a mixture of 4‐vinylphenylboronic acid and phenylboronic acid was carried out in THF under various conditions using a di‐μ‐chlorobis [5‐hydroxy‐2‐[1‐(hydroxyimino‐κN)ethyl]phenylκC] palladium(II) dimer, which is a type of cyclopalladated complex, as a catalyst. When BIIR and a small amount (Pd/Br ≈ 1/1000) of complex were used as the substrate and catalyst, respectively, a 4‐vinylphenyl and phenyl group could be introduced to butyl rubber in a high yield. Isomerization of the exo carbon–carbon double bond in BIIR was observed during the coupling reaction to give a cis and trans endo structure. The peroxide curing behavior of the resulting polymer at 170 °C indicated that the polymer could be cured by dicumyl peroxide, and the maximum torque of the resulting material, which reflects the crosslink density, was controllable by the composition of the boronic acids used. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis,Evaluation and Proposed Binding Pose of Substituted Spiro-Oxindole Dihydroquinazolinones as IRAP Inhibitors

Insulin-regulated aminopeptidase (IRAP) is a new potential macromolecular target for drugs aimed for treatment of cognitive disorders. Inhibition of IRAP by angiotensin IV (Ang IV) improves the memory and learning in rats. The majority of the known IRAP inhibitors are peptidic in character and suffer from poor pharmacokinetic properties. Herein, we present a series of small non-peptide IRAP inhibitors derived from a spiro-oxindole dihydroquinazolinone screening hit (pIC₅₀ 5.8). The compounds were synthesized either by a simple microwave (MW)-promoted three-component reaction, or by a two-step one-pot procedure. For decoration of the oxindole ring system, rapid MW-assisted Suzuki-Miyaura cross-couplings (1 min) were performed. A small improvement of potency (pIC₅₀ 6.6 for the most potent compound) and an increased solubility could be achieved. As deduced from computational modelling and MD simulations it is proposed that the S-configuration of the spiro-oxindole dihydroquinazolinones accounts for the inhibition of IRAP.     

E‐1,2‐diarylsulfonylethene—Source for new class of heterocycles

A new class of pyrazolidinediones, isoxazolidinediones, pyrimidinetriones, and thioxopyrimidinediones were synthesized by the reaction of Michael adduct, dimethyl 2‐(1′,2′‐diarylsulfonyl)ethylmalonate with different nucleophiles, hydrazine hydrate, hydroxylamine hydrochloride, and urea derivatives. J. Heterocyclic Chem., 2011.     

Controlling Peptide Self‐Assembly through a Native Chemical Ligation/Desulfurization Strategy

Self‐assembled peptides were synthesized by using a native chemical ligation (NCL)/desulfurization strategy that maintained the chemical diversity of the self‐assembled peptides. Herein, we employed oxo‐ester‐mediated NCL reactions to incorporate cysteine, a cysteine‐based dipeptide, and a sterically hindered unnatural amino acid (penicillamine) into peptides. Self‐assembly of the peptides resulted in the formation of self‐supporting gels. Microscopy analysis indicated the formation of helical nanofibers, which were responsible for the formation of gel matrices. The self‐assembly of the ligated peptides was governed by covalent and non‐covalent interactions, as confirmed by FTIR, CD, fluorescence spectroscopy, and MS (ESI) analyses. Peptide disassembly was induced by desulfurization reactions with tris(2‐carboxyethyl)phosphine (TCEP) and glutathione at 80 °C. Desulfurization reactions of the ligated peptides converted the Cys and penicillamine functionalities into Ala and Val moieties, respectively. The self‐supporting gels showed significant shear‐thinning and thixotropic properties.     

Improved lithium cyclability and storage in mesoporous SnO2 electronically wired with very low concentrations (≤1 %) of reduced graphene oxide

On the wire: Mesoporous tin dioxide (SnO(2)) wired with very low amounts (≤1?%) of reduced graphene oxide (rGO) exhibits a remarkable improvement in lithium-ion battery performance over bare mesoporous or solid nanoparticles of SnO(2). Reversible lithium intercalation into SnO(2)/SnO over several cycles was demonstrated in addition to conventional reversible lithium storage by an alloying reaction.     

Regiochemical effects on molecular stability: a mechanochemical evaluation of 1,4- and 1,5-disubstituted triazoles

Poly(methyl acrylate) chains of varying molecular weight were grown from 1,4- as well as 1,5-disubstituted 1,2,3-triazoles. Irradiating acetonitrile solutions of these polymers with ultrasound resulted in the formal cycloreversion of the triazole units, as determined by a variety of spectroscopic and chemical labeling techniques. The aforementioned reactions were monitored over time, and the rate constant for the cycloreversion of the 1,5-disubstituted triazole was measured to be 1.2 times larger than that of the 1,4-disubstituted congener. The difference was attributed to the increased mechanical deformability of the 1,5-regioisomer as compared to the 1,4-isomer. This interpretation was further supported by computational studies, which employed extended Bell theory to predict the force dependence of the activation barriers for the cycloreversions of both isomers.     

Incoherent scattering functions of 145 keV gamma rays by K-shell electrons in Y,Ag and Au

The values of incoherent scattering functions are determined experimentally for 145 keV gamma rays in elements Au, Ag and Y at scattering angles 40°, 70° and 100°, using a x-ray gamma coincidence technique. The corresponding theoretical values are obtained from the tabulations of Hubbellet al, and computed from the models of Jauch and Rohrlich and Shimizuet al. A comparison between the theoretical and experimental results showed that the non-relativistic approach adopted in the theory of Shimizuet al is inapplicable to the present cases. A gross agreement is noticed between the present experimental results and the other theoretical values.     

Studies on the constituents of bocconia cordata. IV. Transformation of sanguinarine into bocconine

Nitration of ethoxysanguinarine with equimolar potassium nitrate and sulfuric acid, followed by treatment with sodium hydroxide and methanol, gives 10-nitromethoxysanguinarine. Successive hydrogenation, diazotization and methanolysis convert 10-nitromethoxysanguinarine into bocconine.