1,3-Dipolar cycloadditions of new 2,5-bifunctionalized five-membered cyclic nitrones

A new family of five-membered cyclic nitrones bearing functional groups at positions 2 and 5 were tested in 1,3-cycloadditions with various dipolarophiles. These reactions gave the corresponding cycloadducts as single diastereomers in high yields. The reaction scope was examined, 23 compounds were isolated and fully characterized. The comparison of the reactivity was carried out by a study of reaction conversions while different nitrones or dipolarophiles were used. In addition, the exceptional reactivity of nitrone bearing benzylamino group in position 2 was studied. The formation of the nitrone complex and evaluation of its reactivity in 1,3-DC is presented.     

Nitroxide mediated synthesis of low dispersity random copolymers for low‐loss optical waveguides

Candidate materials for low‐loss optical waveguides based on poly(glycidyl methacrylate‐ran‐pentafluostyrene) [P(GMA‐ran‐PFS)] copolymers were synthesized by nitroxide mediated polymerization (NMP) initiated with BlocBuilder^® [N‐(2‐methylpropyl)‐N‐(1‐diethlphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2‐yl) hydroxylamine] bearing a succinimidyl ester group (NHS‐BlocBuilder) at 90 °C in 1,4 dioxane. The copolymerizations yielded copolymers with low dispersity M_w/M_n between 1.2 and 1.4. The core structure of single‐mode channel waveguides was fabricated by direct UV lithographic patterning. The copolymers with low M_w/M_n resulted in line width roughness (LWR) of about 0.16 μm, whereas LWR of copolymers with M_w/M_n=3.5 but similar compositions was about 0.5 μm. The improvement in microstructural control allotted by NMP permitted finer pattern replication for copolymers desired for optical waveguides, as suggested for photoresist polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2970–2978     

HPLC analysis of a syrup containing nimesulide and its hydrolytic degradation product

The present paper deals with the evaluation of nimesulide, 2-phenoxy-4-nitroaniline, the main hydrolytic degradation product of nimesulide, of methylparaben and propylparaben, and eventually of 4-hydroxybenzoic acid by HPLC with UV detection at 254 nm in syrup as a pharmaceutical formulation. HPLC analysis was employed on the reversed phase C18 with methanol and 0.01 M dibasic ammonium phosphate (ρ _r = 60: 40, pH 4.0). Validation was performed using standards and a pharmaceutical preparation containing the compounds described above.     

On Possible Singular Solutions to the Navier — Stokes Equations

In this paper, we exclude the possibility of existence of a singular solution of the selfsimilar type proposed by Jean Leray More precisely, using a slightly stronger hypothesis we give a simpler proof to the analogous result established by J. Ne?as, M. Rú?i?ka and V. ?verák. We also discuss the possible existence of a singular solution of pseudo-selfsimilar type.     

Steady Plane Flow of Viscoelastic Fluid Past an Obstacle

We consider the steady plane flow of certain classes of viscoelastic fluids in exterior domains with a non-zero velocity prescribed at infinity. We study existence as well as asymptotic behaviour of solutions near infinity and show that for sufficiently small data the solution decays near infinity as fast as the fundamental solution to the Oseen problem.     

The study of Mössbauer effect in EuBa2Cu3O7-y

EuBa₂(Cu_1-xFe_x)₃O_7-x has been investigated by the⁵⁷Fe and¹⁵¹Eu Mössbauer effect. The⁵⁷Fe Mössbauer spectra of the EuBa₂(Cu_1xFe_x)₃O_7-y without or with DC electric current (the current strength I=0.5A) around the superconducting transition temperature have been measured. The results indicate that the isomer shift (IS) and the quadrupole splitting (QS) of the Fe replacing the Cu(2) vary neither with increasing the Fe content nor with the small DC eletric, current passing the superconductor and that the IS and the QS of the Fe replacing the Cu(1) vary with the Fe content. Especially, the IS and the QS of the Fe (D3) replacing the Cu(1) are changed when the small electric current passes the superconductor at 80K.     

Palladium(II)‐Catalyzed meta‐CH Olefination: Constructing Multisubstituted Arenes through Homo‐Diolefination and Sequential Hetero‐Diolefination

Divinylbenzene derivatives represent an important class of molecular building blocks in organic chemistry and materials science. Reported herein is the palladium‐catalyzed synthesis of divinylbenzenes by meta‐C? H olefination of sulfone‐based arenes. Successful sequential olefinations in a position‐selective manner provided a novel route for the synthesis of hetero‐dialkenylated products, which are difficult to access using conventional methods. Additionally, 1,3,5‐trialkenylated compounds can be generated upon successful removal of the directing group.     

Using controlled radical polymerization to confirm the lower critical solution temperature of an N‐(alkoxyalkyl) acrylamide polymer in aqueous solution

N‐(3‐Methoxypropyl) acrylamide (MPAM) was polymerized by controlled radical polymerization (CRP) methods such as nitroxide‐mediated polymerization (NMP) and reversible addition–fragmentation chain‐transfer polymerization (RAFT). CRP was expected to yield well‐defined polymers with sharp lower critical solution temperature (LCST) transitions. NMP with the BlocBuilder (2‐([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino]oxy)‐2‐methylpropanoic acid) and SG1 ([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino] oxidanyl) initiating system revealed low yields and lack of control (high dispersity, ? ～ 1.5–1.6, and inhibition of chain growth). However, RAFT was far more effective, with linear number average molecular weight, , versus conversion, X, plots, low ? ～ 1.2–1.4 and the ability to form block copolymers using N,N‐diethylacrylamide (DEAAM) as the second monomer. Poly(MPAM) (with = 13.7–25.3 kg mol^?1) thermoresponsive behavior in aqueous media revealed cloud point temperatures (CPT)s between 73 and 92 °C depending on solution concentration (ranging from 1 to 3 wt %). The and the molecular weight distribution were the key factors determining the CPT and the sharpness of the response, respectively. Poly(MPAM)‐b‐poly(DEAAM) block copolymer ( = 22.3 kg mol^?1, ? = 1.41, molar composition F_DEAAM = 0.38) revealed dual LCSTs with both segments revealing distinctive CPTs (at 75 and 37 °C for poly(MPAM) and poly(DEAAM) blocks, respectively) by both UV–Vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 59–67