Electrochemical homocoupling of 2-bromomethylpyridines catalyzed by nickel complexes

2,2'-Bipyridine (bpy) and a series of dimethyl-2,2'-bipyridines were synthesized from 2-bromopyridine and 2-bromomethylpyridines, respectively, using an electrochemical process catalyzed by nickel complexes. The method is simple and efficient, with isolated yields between 58 and 98% according to the structure. We first studied the influence of the presence and the position of the methyl group on the yield, using N,N-dimethylformamide (DMF) or acetonitrile (AN) as the solvent, NiBr(2)bpy as the catalyst, and Zn as the sacrificial anode, in an undivided cell and at ambient temperature. On the basis of a better understanding of the reaction mechanism based on electroanalytical studies, we could improve the dimerization both by substituting the catalyst ligand (bpy) by the reagent itself, i.e., 2-bromomethylpyridine or 2-bromopyridine, and by using Fe instead of Zn as the sacrificial anode.     

Macromolecular design of new cationic polyelectrolytes

Methods were elaborated for the synthesis of new monomers, derivatives of diallylguanidine and macromers, which contain fragments of polytetrahydrofuran and diallylic nitrogencontaining end groups (diallylamine, alkyldiallylammonium, diallylguanidine both in base and acetate forms). Alkylation of a macromer with a diallylamine end group was carried out with methyl iodide in various organic solvents. The possibility of synthesis of diallylguanidine acetate homopolymer as well as its statistical copolymer with diallyldimethylammonium chloride was shown. For the first time, block copolymers based on synthesized macromers were obtained.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1976–1982, November, 1994.The work was supported in part by the Russian Foundation For Basic Research (project code 94-03-08924a).     

Cyanogen chloride: self-broadening and intensities in the region of 13 microm

This work presents a synthesis of our results concerning line intensities and self-broadening coefficients for ClCN in the diad (nu1, 2nu 2 0). Absolute band strengths have been determined. The influence of the perturbation in these band strengths due to a Fermi resonance between the 10(0)0 and 02(0)0 levels has been analyzed.     

Iron-mediated electrochemical reaction of alpha-chloroesters with carbonyl compounds

[reaction: see text] Reformatsky-type reactions have been performed efficiently using an electroassisted iron-complex catalysis. Valuable product such as beta-hydroxyesters, ketones or nitriles are thus prepared with high yields.     

Mass spectra of 2,2′-bridged biphenyls with 12-membered heterocyclic bridging rings: 2—some tetrabenzo[b,d, h,j][1, 6]diazacyclododecines

Mass spectra of four tetrabenzo[b, d, h, j][1, 6]diazacyclododecines are reported. The common pattern of fragmentation is altered by the presence of ortho methoxycarbonyl groups.     

Reconstructing arbitrary strain distributions within fiber gratings by time-frequency signal analysis

We apply time-frequency signal-analysis techniques to recover arbitrary distributions of axial strain along a fiber grating from its reflection spectral response. The proposed method permits accurate strain reconstruction with no restrictions on the applied strain profile or on the grating length. We demonstrate the validity and accuracy of the technique by reconstructing the strain field in a fiber grating with a nonmonotonic strain profile, which includes all the following: a constant strain section, high gradient variations, and strain discontinuities.     

Self-broadening coefficients and absolute line intensities in the ν4 + ν5 band of acetylene

Self-broadening coefficients and line strengths have been measured at room temperature for 30 lines of C₂H₂ in the P and R branches of the ν₄ + ν₅ band, using a tunable diode laser spectrometer. These lines, ranging from P(22) to R(23), are located in the spectral range 1275-1390 cm⁻¹. A semiclassical calculation of the line broadenings has been performed considering the main electrostatic interactions and an anisotropic dispersion contribution leading to results in satisfactory agreement with the experimental data.     

Ethylene Polymerization‐Induced Self‐Assembly (PISA) of Poly(ethylene oxide)‐block‐polyethylene Copolymers via RAFT

Poly(ethylene oxide) (PEO) with dithiocarbamate chain ends (PEO–SC(=S)?N(CH₃)Ph and PEO–SC(=S)?NPh₂, named PEO‐1 and PEO‐2 , respectively) were used as macromolecular chain‐transfer agents (macro‐CTAs) to mediate the reversible addition–fragmentation chain transfer (RAFT) polymerization of ethylene in dimethyl carbonate (DMC) under relatively mild conditions (80 °C, 80 bar). While only a slow consumption of PEO‐1 was observed, the rapid consumption of PEO‐2 led to a clean chain extension and the formation of a polyethylene (PE) segment. Upon polymerization, the resulting block copolymers PEO‐b‐PE self‐assembled into nanometric objects according to a polymerization‐induced self‐assembly (PISA).