Synthesis and reactivity of thiophene palladium and thiophene dipalladium complexes with unsaturated molecules

Reactions of 2,5‐dibromothiophene, 1 , with [Pd₂(dba)₃]^?dba [Pd(dba)₂; dba = dibenzylideneacetone] in the presence of N‐donor ligands such as 2,2′‐bipyridine (bpy) and 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine (dtbbpy) give arylpalladium complexes of cis‐[2‐(5‐BrC₄H₂S)PdBrL₂], 2a, b [L₂ = bpy ( 2a ), L₂ = dtbbpy ( 2b )], and cis‐cis‐L₂PdBr[2,5‐(C₄H₂S‐)PdBr(L₂)], 3a, b [L₂ = bpy ( 3a ), L₂ = dtbbpy ( 3b )]. Treatment of cis complexes 2a, b and 3a, b with CO causes the insertion of CO into the Pd? C bond to give the aroyl derivatives of palladium complexes of cis‐[2‐(5‐BrC₄H₂S)COPdBrL₂], 4a, b [L₂ = bpy ( 4a ), L₂ = dtbbpy ( 4b )], and cis‐cis‐[(L₂)(CO)BrPdC₄H₂S‐PdBr(CO)(L₂)], 5a, b [L₂ = bpy ( 5a ) and L₂ = dtbbpy ( 5b )], respectively. Treating complexes 2a, b with 1 mole equivalent of isocyanide XyNC (Xy = 2,6‐dimethylphenyl) gave iminoacyl complexes cis‐[2‐(5‐BrC₄H₂S)C?NXyPdBrL₂], 6a, b [L₂ = bpy ( 6a ), L₂ = dtbbpy ( 6b )], and a 3‐fold excess of isocyanide XyNC (Xy = 2,6‐dimethylphenyl) gave triiminoacyl complexes [2‐(5‐BrC₄H₂S)(C?NXy)₃ PdBr], 7 . Cyclization reactions of 6a, b with 3 mole equivalents of isocyanide XyNC (Xy = 2,6‐dimethylphenyl) or cyclization reaction of 7 with 1 mole equivalent of isocyanide XyNC (Xy = 2,6‐dimethylphenyl) both gave tetraiminoacyl complexes of [2‐(5‐BrC₄H₂S)(C?NXy)₄PdBr], 8 , which was also obtained by the reaction of 1 or 2a, b with a 4‐fold excess of isocyanide XyNC with or without add Pd(dba)₂. Similarly, complexes 3a and b were also reacted with 2 mole equivalents of isocyanide XyNC (Xy = 2,6‐dimethylphenyl) to give iminoacyl complexes cis‐cis‐[(L₂)(CNXy)BrPdC₄H₂S‐PdBr(CNXy)(L₂)], 10a, b [L₂ = bpy ( 10a ), L₂ = dtbbpy ( 10b )] and an 8‐fold excess of isocyanide XyNC (Xy = 2,6‐dimethylphenyl) afforded tetraiminoacyl complexes of [2,5‐(C₄H₂S)(C?NXy)₈Pd₂Br₂], 11 . Complexes 2a, b and 3a, b reacted with TlOTf [(TfO = CF₃SO₃)] in CH₂Cl₂ to give 9a, b and 12a, b , respectively, in a moderate yield. Copyright © 2007 John Wiley & Sons, Ltd.     

Studies on 3,5-diaminopyrazole derivatives

The behaviour of 3,5-diamino-4-phenylazopyrazole toward a variety of reagents is reported. Several new 3,5-diaminopyrazole derivatives as well as amino derivatives of fused pyrazoles have been prepared.

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Untersuchungen an 3,5-Diaminopyrazol-Derivaten

Zusammenfassung Es wird über das Verhalten von 3,5-Diamino-4-phenylazopyrazol gegenüber verschiedenen Agentien berichtet. Es wurden sowohl einige neue 3,5-Diaminooyrazol-Derivate als auch einige Aminoderivate von kondensierten Pyrazolen dargestellt.

     

Cycloshydratation de dios in presence D'HMPT

1,4 and 1,5-diols heated with 0.3 equivalent of HMPA undergo cyclodehydration leading to tetrahydrofurans and tetrahydropyrans.     

Base-catalyzed isomerization of phenylpropenes

The prototropic rearrangement of 3-phenyl-1-propenes to the corresponding 1-phenyl-1-propenes was investigated in basic media utilizing 0.1M sodium ethoxide in absolute ethanol at 81°C. It was found that the effect of substituents on the rate of such isomerizations follows the order: p-NO₂ > o-Cl > m-Cl ≥ m-F > p-Br > o-CH₃ > m-CH₃ > m-CH(CH₃)₂ > p-CH(CH₃)₂ ≥ p-C(CH₃)₃ > o-OCH₃. This is consistent with first-order kinetics and “BS” mechanism. Quantitative treatment in terms of Hammett's equation showed a straight line, with a slope (p value) of +2.25. An increase in the strength of the base was also found to cause an increase in the rate of isomerization.     

Validated polarographic methods for the determination of certain antibacterial drugs.

Two simple, precise, inexpensive and sensitive voltammetric methods for the determination of lomefloxacin (LFX), sparfloxacin hydrochloride (SFX), gatifloxacin (GFX), and moxifloxacin (MFX) were developed. The present methods were first used to explore the adsorption behavior of the four investigated antibacterial agents at a hanging mercury dropping electrode (HMDE), by a direct method and secondly by a modification via their complexation with PdCl(2). For the direct method, drugs were accumulated on HMDE, and a well-defined reduction peak was obtained in Britton-Robinson buffer of pH 7 for LFX and SFX, and pH 6 for GFX and MFX. The adsorptive stripping response was evaluated as a function of some variables such as the scan rate, pH, accumulation time and potential. For the modified method, the adsorptive behavior of Pd(II)-4-quinolone complexes at the HMDE developed a strippining voltammetry peak at a more negative potential than that of the free Pd(II) ions (-1.05 V). The limits of detection (LOD) were 2 x 10(-8) M, while the limits of quantification (LOQ) were 6 x 10(-8) M for the investigated drugs. The methods were applied to the determination of LFX, SFX, GFX, and MFX in biological samples and pharmaceutical preparations, and also compared with the official reference methods. Complete validation of the proposed methods was also done.     

Non-Destructive neutron activation analysis of zircons from different genetic types

Twelve zircon samples representing different genetic types from Australia, China, Egypt, Hungary, Korea and Nigeria were examined using the neutron activation techniques. The study of the trace elements encountered in zircons, especially Zr/Hf ratios, shed the light on the type of zircon minerals as well as the mother rock from which zircons wrre separated. Furthermore, the effect of the secondary processes on zircons and their host rocks were also studied.     

A graphical method for determing the coefficient of viscosity of Newtonian liquids using an oscillating cylinder viscometer

Zusammenfassung Es wird ein zweites graphisches Verfahren dargestellt, welches gestattet, die Viskosität zäher Flüssigkeiten zu ermitteln.     

Anomalies in Elastic Scattering at Isobaric Analogue States

Excitation functions for proton elastic scattering on Mn⁵⁵ at proton energies from 1320 KeV to 1480 KeV have been measured at the angles 135° and 150°. Anomalies in the differential elastic scattering were observed at E_p = 1350 ± 4 KeV, 1385 ± 4 KeV and 1445 ± 4 KeV respectively. These resonance states are the isobaric analogues of the ground, first excited and second excited states in Mn⁵⁶ respectively. Analysis of the results showed that these resonance states are best fitted to a J^π = 3⁺, 2⁺ and 1⁺ which is in excellent agreement with the J^π values of the corresponding states in Mn⁵⁶. The total widths and proton widths of these states were determined.     

13C NMR study of N-unsubstituted aziridines: I—steric effects,pseudoconjugation

¹³C chemical shifts for twenty-nine alkyl and phenyl substituted N-unsubstituted aziridines have been measured. Additivity parameters for methyl, phenyl and aziridyl carbons have been derived with the aim of testing the consistency of the assignments made on the basis of chemical shift considerations and off-resonance decoupling information. The observed chemical shifts are discussed in terms of steric and pseudoconjugation effects.