Diazo-, azo-, and azidoazoles. VII. Imidazo[1,2-b]- versus imidazo[2,1-c]benzo-as-triazines

Treatment of 3-aminobenzo-as-triazines with bromoacetaldehyde ethylene acetal give linear tricyclic imidazobenzo-as-triazines, where 3-amino-7-methylbenzo-as-triazine 1-oxide yields the angular isomer. The structures of these compounds have been established by comparing their nmr spectra to those of pyrazolo [5,1-c]- and s-triazolo[5,1-c]benzo-as-triazines obtained form the appropriate azo derivatives by intramolecular cyclization.     

Some first passage time problems for shot noise processes

It has recently been shown that the first passage time problem for a certain class of one-dimensional processes that includes shot noise can be formulated in terms of a set of integral equations. These are found by exact enumeration of all possible trajectories. We show that the equations can be found by more direct means for processes described by the evolution equation , wheren(t) is time-localized shot noise.     

Highly selective synthesis of 2-substituted-5-hydroxy-6-oxo-1,6-dihydropyrimidine-4-carboxylic acid derivatives using a novel protected dihydroxyfumarate

A high yielding (50-96%) route to 2-substituted-5-hydroxy-6-oxo-1,6-dihydropyrimidine-4-carboxylic acid derivatives has been developed using a rationally designed dihydroxyfumarate derivative. The fully unprotected pyrimidinone heterocycle was prepared in quantitative yield upon treatment with HCl.     

Dinuclear complexes with a μ-cyano ligand. part IX. synthesis,characterization and magnetic studies of several derivatives of [Cr(CN)6]3− and [Cr(NO)(CN)5]3−

Summary Twelve dinuclear complexes, each with a bridging cyano group, of formulaecis-M[(aa)₂FCr-NC-Cr(CN)₅] andcis- M[(aa)₂FCr-NC-CrNO(CN)₄] (aa=ethylenediamine or 1,3-diaminopropane; M=K⁺, Na⁺ or NH ₄ ⁺ ) have been prepared by solid state heating of the corresponding doubly complexed saltstrans-M[CrF(H₂O)(aa)₂][Cr(CN)₆] andtrans-M [CrF(H₂O)(aa)₂][CrNO(CN)₅]. All have been characterized by chemical analysis, electronic and i.r. spectra and conductivity measurements.Magnetic susceptibilities down to liquid helium temperature have been determined forcis-K[(en)₂FCr-NC-Cr(CN)₅],cis-K[(tn)₂FCr-NC-Cr(CN)₅] andcis-K[(en)₂FCr-NC-CrNO-(CN)₄]. Slight antiferromagnetic interactions have been found in the first two compounds (J=–1.4 and –1.2 cm^–1, respectively). Thecis-K[(en)₂FCr-NC-CrNO(CN)₄] compound behaves as a Curie paramagnet and a structural model is proposed to explain this fact.     

Diazo-, azo- et azidoazoles. III. Tautoméric azido/tétrazole dans des nouveaux azidoazoles

Some derivatives of 2-azidoimidazole and 3(5)azido-s-triazole were prepared to investigate the possibility of an azido/tetrazole equilibrium in these compounds. An explanation for observed differences in azido/tetrazole equilibrium between azole series and azine or thiazole series is suggested.     

A new method for the preparation of modified oligonucleotides

[reaction-see text] N-Nitrothymidine can be transformed into a phosphoramidite building block suitable for oligonucleotide synthesis using the standard phosphite triester solid-phase approach. The N-nitrothymidine residues remain stable during the elongation cycles and react smoothly with primary amines, furnishing oligonucleotides containing N3-modified thymidines. A number of N3-substituted oligonucleotides have been prepared using this methodology, some of them incorporating aminoalkyl or hydroxyalkyl groups.     

New fluorescence PET systems based on N2S2 pyridine-anthracene-containing macrocyclic ligands. spectrophotometric, spectrofluorimetric, and metal ion binding studies

Three new fluorescent devices for protons and metal ions have been synthesized and characterized, and their photophysical properties have been explored; these are the macrocycles 7-(9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1) and 7-(10-methyl-9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L2) and the bis macrocycle 7,7'-[9,10-anthracenediylbis(methylene)]bis-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L3). All these systems have a pyridil-thioether-containing macrocycles as a binding site and an anthracene moiety as a signaling agent. The coordination properties of these ligands toward Cu(II), Co(II), Ni(II), Zn(II), and Pd(II) have been studied in solution and in the solid state. The addition of these metal ions to dichloromethane solutions of L1, L2, and L3 produce strong changes in the absorption and emission spectra of these ligands. The stoichiometry of the species, formed at 298 K, have been determined from absorption and fluorescence titrations. The Co(II) and Cu(II) complexes of L1 have been studied by EPR spectroscopy. This last complex and its free ligand have also been characterized by X-ray crystallography.