Efficient methods for the synthesis of 2-hydroxyphenazine based on the Pd-catalyzed N-arylation of aryl bromides

[reaction: see text] Substituted diphenylamines can be synthesized by Pd(0)-catalyzed N-arylation using o-nitroanilines and nitro-substituted aryl bromides for a substrate. Cyclization of the diphenylamines by various methods, including the intramolecular Pd(0)-catalyzed N-arylation, produces 2-methoxyphenazine which can easily be deprotected to give 2-hydroxyphenazine. This phenazine is required to synthesize methanophenazine, a novel redoxactive cofactor isolated from methanogenic archaea.     

Surface light-scattering at the air-liquid interface: from newtonian to viscoelastic polymer solutions

The dynamics of the liquid-air interface of aqueous solutions of a tensioactive triblock copolymer (Pluronic F-68) has been studied using surface quasielastic light scattering over a broad range of concentrations and temperatures. Ancillary surface tension and bulk rheometry data have been obtained for the same system. The results show that the classical theoretical spectrum for monolayers on a Newtonian fluid can be applied only for concentrations below 4.10(-2) mM. For concentrations above c = 14 mM a clear peak centered at zero frequency appears in the spectrum. This feature is incompatible with the classical theoretical spectrum. The SQELS spectra have been described in terms of the theory of Wang and Huang [Wang, C. H.; Huang, Q. R. J. Chem. Phys. 1997, 107, 5898] considering that the loss modulus of the concentrated solutions shows the existence of two relaxation modes even at low frequencies. The theory is able to explain the existence of a peak centered at zero frequency in the spectra, and the theoretical spectra point out the existence of an elastic peak together with the capillary one. There is a reasonable agreement between the relaxation times and the product Gtau obtained from the fits of the SQELS spectra to the theory of Wang and Huang and those obtained from bulk rheology.     

The rank of a commutative cancellative semigroup

Summary For a commutative cancellative semigroup S, we define the rank of S intrinsically. This definition implies that the rank of S equals the usual rank of its group of quotients. We also characterize the rank in terms of embeddability into a rational vector space of the greatest power cancellative image of S.     

X-Ray crystal structure of the tris(acetato)dioxoosmate(VI) anion

X-ray crystallographic study of K[OsO₂(O₂CMe)₃]· 2MeCO₂H shows that the anion has cis dioxo, one chelate and two trans monodentate acetato groups.     

Novel reactions of carbon suboxide. Synthesis of 1,5-benzodioxepins, 1,5-benzoxathiepins and 1,5-benzoxazepins

The preparation of 1,5-benzodioxepins, 1,5-benzoxathiepins and 1,5-benzoxazepins derivatives is described here. The structure of the products has been determined by elemental analysis and spectroscopic data.     

Prediction of proton magnetic resonance shifts: The dependence on hydrogen charges obtained by iterative partial equalization of orbital electronegativity

Proton chemical shifts correlate linearly with charges on hydrogen obtained by a method for iterative partial equalization of orbital electronegativity. The compounds studied comprise a wide variety of classes of molecules; all points fall on a single correlation line, showing the general importance of electronic effects in proton chemical shifts and the physical significance of the atomic charges. On the other hand, as there is no general correlation between charges on carbon and on hydrogen atoms, proton chemical shifts cannot be used as probes for charge densities on carbon atoms. Deviations from the correlation line can be attributed to anisotropy effects and provide an estimate for their magnitude.     

Hydrogenation and halogenation of 6-phenyl-5-azabenzo[f]fluoranthene and reduction of its adducts with acrylonitrile

The hydrogenation of 6-phenyl-5-azabenzo[f]fluoranthene in the presence of rhenium heptasulfide takes place in the meso positions of its azaanthracene fragment. The reaction of 5-azabenzo[f]fluoranthene with acid chlorides and aluminum chloride in nitrobenzene gives its 8-chloro derivative. The reduction of the adducts of the diene synthesis of 6-phenyl-5-azabenzo[f]fluoranthene with acrylonitrile by means of sodium in butyl alcohol leads to the corresponding aminomethyl derivatives and a product of retrodiene synthesis, viz., the starting azabenzofluoranthene. The reduction of the adduct of the diene synthesis of 1,3-diphenyl-2-azaanthracene with acrylonitrile proceeds similarly.Translated from Khimiya Geterotsikllcheskikh Soedinenii, No. 2, pp. 233–235, February, 1982.