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The development of new chemical transformations based on catalytic functionalization of unactivated C-H bonds has the potential to simplify the synthesis of complex molecules dramatically. Transition metal catalysis has emerged as a powerful tool with which to convert these unreactive bonds into carbon--carbon and carbon--heteroatom bonds (1-6), but the selective transformation of aliphatic C-H bonds is still a challenge. The most successful approaches involve a 'directing group', which positions the metal catalyst near a particular C-H bond, so that the C-H functionalization step occurs via cyclometallation (7). Most directed aliphatic C-H activation processes proceed through a five-membered-ring cyclometallated intermediate (8-10). Considering the number of new reactions that have arisen from such intermediates, it seems likely that identification of distinct cyclometallation pathways would lead to the development of other useful chemical transformations (11). Here we report a palladium-catalysed C-H bond activation mode that proceeds through a four-membered-ring cyclopalladation pathway. The chemistry described here leads to the selective transformation of a methyl group that is adjacent to an unprotected secondary amine into a synthetically versatile nitrogen heterocycle. The scope of this previously unknown bond disconnection is highlighted through the development of C-H amination and carbonylation processes, leading to the synthesis of aziridines and β-lactams (respectively), and is suggestive of a generic C-H functionalization platform that could simplify the synthesis of aliphatic secondary amines, a class of small molecules that are particularly important features of many pharmaceutical agents., Several classes of directing group can participate in directed C-H activation of aliphatic systems and include functionalities such as carbonyl derivatives, aromatic nitrogen heterocycles and hydroxyl motifs (12-18). Palladium salts [...]

In this article, we analyzed the influence of isosorbide content on glass transition temperature and crystallinity of poly(L-lactide). Different synthesis methods were applied to determine optimal procedure for polymerization of L-lactide in the presence of isosorbide. Two procedures were performed with tin(II) 2-ethylhexa-noate as the catalyst: first, using the vacuum sealed vessel, and second, using microwave reactor bulk polymerizations. The solution polymerization (with trifluoromethanesulfonic acid as catalyst) was possible at the temperature of 40°C. Obtained polyesters had number average molecular weights ranging from 20,000 to 65,000 g [mol.sup.1], according to the gel permeation chromatography measurements. The polymer structure was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Thermal properties of the obtained polymers were analyzed using thermogravimetry (TG) and differential scanning calorimetry (DSC). According to DSC measurements, the addition of isosorbide in the polyesters influenced the increase in both glass transition temperature and degree of crystallization for all samples. The results obtained by thermogravimetric analysis confirmed the strong influence of polymerization mechanism on synthesized poly(L-lactides) thermal properties. POLYM. ENG. SCI., 53:1374-1382, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Because of concerns for the global environment biodegradable polymers became appropriate alternatives for many petrochemical-based polymers. Bio-renewable and biodegradable materials, such as lactide (1) or isosorbide, are becoming more [...]

Abstract: Several new ditopic receptors have been synthesized from 4,4'-bis(methoxyphenyl)glycoluril (1). The first receptor site is a cleft composed of two fused 2-imidazolone rings, which are flanked by two aromatic [...]

The opportunistic pathogen Pseudomonas aeruginosa produces colorful, redox-active antibiotics called phenazines. Excretion of pyocyanin, the best-studied natural phenazine, is responsible for the bluish tint of sputum and pus associated with P. aeruginosa infections in humans. Although the toxicity of pyocyanin for other bacteria, as well as its role in eukaryotic infection, has been studied extensively, the physiological relevance of pyocyanin metabolism for the producing organism is not well understood. Pyocyanin reduction by P. aeruginosa PAl4 is readily observed in standing liquid cultures that have consumed all of the oxygen in the medium. We investigated the physiological consequences of pyocyanin reduction by assaying intracellular concentrations of NADH and NA[D.sup.+] in the wild-type strain and a mutant defective in phenazine production. We found that the mutant accumulated more NADH in stationary phase than the wild type. This increased accumulation correlated with a decrease in oxygen availability and was relieved by the addition of nitrate. Pyocyanin addition to a phenazine-null mutant also decreased intracellular NADH levels, suggesting that pyocyanin reduction facilitates redox balancing in the absence of other electron acceptors. Analysis of extracellular organic acids revealed that pyocyanin stimulated stationary-phase pyruvate excretion in P. aeruginosa PAl4, indicating that pyocyanin may also influence the intraceilular redox state by decreasing carbon flux through central metabolic pathways.

SYNTHESIS OF PHARMACEUTICAL DERIVATIVES FROM ETRAHYDROFURAN. Chris Colanero * and George Kvakovszky, Christian Brothers University, Memphis, Tennessee, and Pennakem, Memphis, Tennessee. Organic synthesis of a series of three substituated tetrahydrofurans [...]

The temporary axion states of gas- phase furan, isoxzole, oxazole, pyrrole, pyrazole, imidazole, thiophene, isothiazole, and thiazole were characterized by means of eletctron transmission spectroscopy. The measured energies of vertical electron attachment were compared with the virtual orbital energies of the neutral state molecules supplied by MP2 and B3LYP calculations with the 6 - 31G* basic set.

The photochemistry of some 3-N-alkylamino-5-perflouoroalkyl-1,2,4-oxadiazoles in the presence of nitrogen nucleophiles is investigated. Comments on the photoreactivity of flourinated oxadiazoles and on the applications of these photoprocesses in the synthesis of target flourinated structures are emphasized.