Condensed 1,2,4-triazines. Regioselective condensations with benzo[h]quinoline-5,6-dione

Benzo[h]quinoline-5,6-dione condenses with semicarbazide and its derivatives regioselectively at the 6-position and the products cyclize into the corresponding condensed 1,2,4-triazines. Reactions of the obtained triazines with a variety of reagents are described.     

31P chemical shifts in N-aryliminotriphenylphosphoranes

³¹P chemical shifts in N-aryliminotriphenylphosphoranes and the corresponding N-methylated phosphonium salts are presented. They can be correlated with those theories of the bonding in phosphorus-nitrogen ylides which involve partial double bonding as a result of p^π–d^π overlap.     

Complexes of vitamin B6 XII : Mixed ligand complexes of some divalent metal ions with pyridoxamine and histidine

Potentiometric pH titrations (I = 0.15 M NaNO₃; 37°C) have been employed to study the various complex equlibria in the systems involving pyridoxamine and histidine with Co(II), Ni(II), Cu(II), and Zn(II). The stoichiometry and formation constants of different species have been determined with the aid of MINIQUAD-75. The complexes obtained were mostly protonated and positively charged. The formation of the ternary species is discussed in terms of the binary species. They were also correlated with the quaternary species involving pyridoxamine, glycine, and imidazole. Spectral analysis of the complex solutions of different compositions are also reported. The relevance of these ternary complex equilibria to some biological functions is discussed.     

Activated nitriles in heterocyclic synthesis. Part III. Synthesis of N-amino-2-pyridone,pyranopyrazole and thiazolopyridine derivatives

The reaction of 2-cyanoethanoic acid hydrazide and arylidenemalononitrile was studied as a new route for the synthesis of N-amino-2-pyridones. Pyrano[2,3-c]pyrazole and thiazolo[2,3-a]pyridine could be prepared from the reaction of arylideneazolones with the same reagent.     

Studies on arylhydrazonoisoxazolinethiones. Behaviour of 4-arylhydrazono-3-phenyl-2-isoxazoline-5-thiones toward hydrazines,grignard reagents and alkylating agents

The 4-arylhydrazono-3-phenyl-2-isoxazoline-5-thiones 2 react with hydrazines to yield the 5-hydrazones 3 and 5 . The reaction of 2 with Grignard reagent resulted in addition of the reagent to the thiocarbonyl group to yield 7 . Treatment of 2 with diazomethane effected S - and N -methylation beside 1,2,3-triazole derivative 11 obtained through isomerisation. The potassium salt of 2 react with alkyl halides to yield the S-alkyl derivatives 12 .     

Feldionen-Mikroskopie und Massen-Spektroskopie von schwefelbedeckten Ag-Oberfl?chen

Ohne Zusammenfassung     

Triplet quantum yield determination by photosensitized oxygenation in the presence of heavy atom additives: Rhodamine B in methanol

Relative rates of heavy-atom-enhanced photosensitized ¹O₂-reactions may be used to determine φ^o_T of sensitizers in heavy-atom-free solutions. φ^o_T = 0.12 ± 0.02 is obtained for a 5·10^?5 M methanolic solution of Rhodamine B .     

Spectrophotometric determination of some benzothiadiazine diuretics with 7,7,8,8-tetracyanoquinodimethane

A new spectrophotometric method for the determination of some benzothiadiazine drugs is presented, based on reaction with 7,7,8,8-tetracyanoquinodimethane in sodium acetate medium and measurement at 578 nm. Beer's law is obeyed in the concentration range 0.7-6.0 mug/ml for all eight drugs tested.     

Solvent and substituent effects on spectroscopical changes of some diazoaminobenzene derivatives

A series of diazoaminobenzene derivatives (seven) in which the substituents have a wide range of electronic characters are set out to understand the involvement of the substituent identity in controlling the changes in their electronic absorption spectra. The interactions between the diazoamino group and the different groups account for some spectral shifts. The UV-vis spectrum of each compound is measured in several solvents with wide variations of solvent polarity parameters to examine the role of the chemistry of the solvent in these spectroscopical changes. The electronic transitions are assigned and the solvent induced spectral shifts are analyzed in relation to the different solute-solvent interaction mechanisms using computational chemistry. The regression analysis is applied for correlating the different parameters. The results help to assign the solute-solvent interactions and the solvatochromic potential of the investigated compounds. It is concluded that the electronic character of the substituent and the chemical nature of the solvent are the major factors for the observed solvatochromism.