Reactions of malonthioamides and malonamidines with methyl acetylpyruvate as a one-step method to prepare 4-thio- and 4-aminopyrrolo[3,4-c]pyridines

We report an efficient one-step approach to 4-thio and 4-aminopyrrolo[3,4-c]pyridines based on the selective reaction of malonthioamides and malonamidines with methyl acetylpyruvate. Structural proof is given by HMBC and HMQC spectra. A cascade heterocyclization mechanism is proposed for the reactions studied.     

Shape resonances in slow electron scattering by aromatic molecules. I. Anthraquinone derivatives

A series of anthraquinone (C(14)O(2)H(8)) derivatives has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), photoelectron spectroscopy (PES), and AM1 quantum chemical calculations. Mean lifetimes of molecular negative ions M(-.) (MNI) have been measured. The mechanism of long-lived MNI formation in the epithermal energy region of incident electrons has been investigated. A simple model of a molecule (a spherical potential well with the repulsive centrifugal term) has been applied for the analysis of the energy dependence of cross sections at the first stage of the electron capture process. It has been shown that a temporary resonance of MNI at the energy approximately 0.5 eV corresponds to a shape resonance with lifetime 1-2.10(-13) s in the f-partial wave (l = 3) of the incident electron. The next resonant state of MNI at the energy approximately 1.7 eV has been associated with the electron excited Feshbach resonance (whose parent state is a triplet npi* transition). In all cases the initial electron state of the MNI relaxes into the ground state by means of a radiationless transition, and the final state of the MNI is a nuclear excited resonance with a lifetime measurable on the mass spectrometry timescale. Copyright 1999 John Wiley & Sons, Ltd.     

Reactions of 5-mercaptoazoles and pyridine-2-thiones with acetylenic esters. Selectivity of the formation of novel fused thiazin-4-ones and thiazolidin-4-ones

A systematic study of the reactions of dimethyl acetylenedicarboxylate (DMAD) and methyl propynoate with 5-mercaptoazoles and pyridine-2-thiones has been carried out and as a result, a number of novel imidazo[1,5-b]thiazin-4-ones 6a,b, pyrazolo[1,5-b] thiazin-4-ones 15a-f, imidazo[1,5-b]thiazol-4-ones 7a,b and thiazolo[3,2-a]pyridines 21a-c have been prepared. The influence of the size of the ring of the starting "cyclic" thioamides on the size of the fused ring in the reaction products has been established. The preferred formation of a six-membered thiazine ring took place in the reactions of 5-mercaptoazoles. In contrast, the five membered thiazolidine ring is formed in reactions of pyridine-2-thiones. In both cases the product is a five-membered ring fused to a six-membered heterocycle.     

Spectroscopic methods for determination of catecholamines: A mini-review

Catecholamines are biogenic compounds that perform a variety of vital functions, playing a key physiological role in humans and animals. They are important markers in diagnosis of diseases and dysfunctions as well as widespread components of pharmaceutical formulations. Therefore, development of highly sensitive, rapid, and economically efficient methods for the determination of catecholamines is of great interest. The spectroscopic analytical methods have a good potential in this respect. This mini-review summarizes in a concise manner some advances and trends in the determination of catecholamines by spectroscopic methods, including spectrophotometry, fluorescence spectroscopy, immunoassays with spectroscopic detection, Raman spectroscopy, and other methods. Information on mainly determined compounds and analyzed samples is given and discussed. Analytical strategies and performance for the quantitation of catecholamines in various samples are described.     

Synthesis, crystal structure, and antitumor activity of the cadmium dichloride complex with semicarbazide

The chelate cadmium dichloride complex with semicarbazide was synthesized. The use of this complex in the cytostatic combination therapy together with cyclophosphamide results in 67% survival of mice and a threefold increase in the average life span of survivors with P-388 leukemia.     

Mechanisms of postsynthesis doping of boron nitride nanostructures with carbon from first-principles simulations

Electron-beam-mediated postsynthesis doping of boron-nitride nanostructures with carbon atoms [Nature (London) 464, 571 (2010); J. Am. Chem. Soc. 132, 13?692 (2010)] was recently demonstrated, thus opening a new way to control the electronic properties of these systems. Using density-functional theory static and dynamic calculations, we show that the substitution process is governed not only by the response of such systems to irradiation, but also by the energetics of the atomic configurations, especially when the system is electrically charged. We suggest using spatially localized electron irradiation for making carbon islands and ribbons embedded into BN sheets. We further study the magnetic and electronic properties of such hybrid nanostructures and show that triangular carbon islands embedded into BN sheets possess magnetic moments, which can be switched on and off by electrically charging the structure.     

Markovian representation of a bilinear time series model and maximum likelihood estimation of the parameters

A bilinear time series (BLTS) model is expressed in the form of Akaike's Markovian representation in order to use the Kalman recursive estimation approach. It is shown that Akaike's Markovian representation of autoregressive moving average models of orderp and q (ARMA(p,q)) and that of the bilinear model are equivalent. This equivalence facilitates the maximum likelihood estimation of the parameters involved in the bilinear model, which otherwise is an unwieldy problem. The present approach can easily be extended to take into account missing observations