Reaction of electron rich heterocycles with electrophiles. Formylation of indoles via thiomethylation

The formylation of indoles 1 by dithiocarbenium-ions 2 is discussed. The reaction proceeds to thioacetals 4 under mild conditions. Longer reaction times yield bisindolylmonomethylcyanines 5–6 . Generally, the reaction is inhibited by the presence of electron-withdrawing groups at the pyrrol nucleus of indole 1 , e.g. an acetyl group.     

Darstellung und Struktur von Pyrazolyl-Kationen mit Polymethin- und Methan-Gerüst

The 4-pyrazoline-3-one1 reacts with 4-dimethylaminobenzaldehyde to yield the stable asymmetric cyanine dye2b which reacts with1 to give the colorless (aryl) (dipyrazolyl) methane3b. Using aldehydes with less cationstabilizing groups the polymethines2 are not isolated but only the methanes3. The structures of2b and3 are discussed by¹ H,¹³C and Hetero NMR spectra.     

The relationship between students' mathematical thinking types and representation preferences in definite integral problems

ABSTRACT

Given that curriculum materials serve as cultural artefacts, this study addresses the need for more research on curriculum materials in different contexts. Most studies concerning curriculum materials have been conducted in US and, therefore little is known about the nature of materials in other cultural-educational contexts. The aim of this paper is to identify the underlying cultural norms of potentially constructed classrooms, by analysing recurrent activities in the most commonly used Finnish teacher guides at primary-school level. We identified three norms embedded in them: (1) creating opportunities for learning through a variety of activities and communication; (2) keeping the class gathered around a specific mathematical topic; and (3) concurrent active involvement of teachers and students. The results add to knowledge about both teacher guides and the Finnish educational context. Moreover, it adds to the growing body of methodologies, as our analytical approach is novel in the context of textual analysis.     

A new donor–acceptor double‐cable carbazole polymer with perylene bisimide pendant group: Synthesis,electrochemical, and photovoltaic properties

We report here electrochemical synthesis of novel soluble donor–acceptor (D–A) polymer with suitably functionalized perylenetetracarboxylic diimide dye derivative covalently linked to carbazole moiety (Cbz‐PDI). The band gap, E_g was measured using UV–Vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Efficient intramolecular electron transfer from carbazole‐donor to perynediimide‐acceptor leads to remarkable fluorescence quenching of the perylene core. Furthermore, spectroelectrochemical property and surface morphology of the polymer film were investigated. Characteristic monoanion and dianion radical bands on the UV–Vis absorption spectra attributed to the electrochemical reduction of the neutral polymer were observed. During the reduction process, red color of the film turned into blue and violet, respectively. Finally, the photovoltaic performance of the D–A double‐cable polymer was checked and nearly 0.1% electrical conversion efficiency is obtained under simulated AM 1.5 solar light with 100 mW/cm² radiation power. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6280–6291, 2009     

Thermal and magnetothermal properties of La0.5Pr0.5Mn2Si2

The thermal and magnetothermal properties of La_0.5Pr_0.5Mn₂Si₂ and isostructural LaFe₂Si₂ intermetallic compounds in the temperature range 4.5-303 K are reported with and without applied magnetic field. The electronic, lattice, and magnetic contributions to the heat capacity of La_0.5Pr_0.5Mn₂Si₂ are determined and analyzed. We have determined and from heat capacity experiments; the values are in line with those from the magnetization measurements. We conclude that in order to observe the anomaly in the heat capacity data around in the system, the transition around should occur in a narrow temperature interval.     

Electrochemical and optical properties of novel donor‐acceptor thiophene‐perylene‐thiophene polymers

In this study, donor‐acceptor type thiophene‐perylene‐thiophene monomers were synthesized and polymerized by both oxidative polymerization using FeCl₃ as catalyst and the electrochemical process. UV–vis, FTIR, ¹H NMR, and elemental analysis techniques were used for structural characterization. Thermal behaviors of these compounds were determined by using TGA system. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and electrochemical and optical band gap values were calculated by using the results of cyclic voltammetry and UV–vis measurements, respectively. The number–average molecular weight (M_n), weight–average molecular weight (M_w), and polydispersity index (PDI) values of synthesized polymers were determined by size exclusion chromatography. Conductivity measurements of these polymers were carried out by electrometer by using a four‐point probe technique. The conductivity was observed to be increased by iodine doping. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1974–1989, 2008     

Silylenolether-Funktionalisierung, 3. Mitt. Regioselektive Acylierung von Trimethylsilylenolethern mit 2-Alkoxy-1,3-dioxolanen — Synthese von α- und γ-geschützten Dicarbonylverbindungen

Acylation of silylenol ethers1 and9 yield with 2-alkoxy-2-alkyl(or aryl)-1,3-dioxolanes5 in a simple way by zinc dichloride-diethyl ether-catalysis regioselectively the - and -protected dicarbonyl derivatives6,7, and10. The enhanced reactivity of the cyclic orthoesters5 in this reaction is discussed in comparison with acyclic reagents. The yield is influenced by steric effects at the reaction center.

     

Zur Reaktion von Phenazon und lithiiertem Phenazon mit Aryl-Carbonyl-Derivaten

Some new experimental results are described on the acid catalysed reaction of the 4-Pyrazoline-3-on (1a) with aromatic aldehydes leading to the cationic derivatives4 and5.4-Pyrazoline-3-on-lithium (1b), synthesised for the first time, gives in good yield with 4-dimethylaminobenzaldehyde under mild condition the cyanine2b and with benzophenone the pyrazolyl-diphenylmethane dye8.

Zur Struktur von2a und4a siehe Lit.².