An efficient strategy of polymorph screening is offered for tert-butylthiacalix[4]arene tetrasubstituted with phenacyloxy groups (1), which is based on saturation of its guest-free solid samples and inclusion compounds with guest...

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Efficient two-step methylviologen (MV2+) — mediated electrosynthesis of a nanocomposite of gold nanoparticles with copper(I) oxide stabilized by a shell of poly(N-vinylpyrrolidone) (Au/Cu2O@PVP) was performed in DMF at room temperature at the potentials of MV.+ radical cation generation. At the first step, the mediated reduction of Cu2+ ions, generated in situ by dissolution of the copper anode, in the presence of dissolved oxygen or with subsequent oxidation with oxygen, leads to Cu2O@PVP composite containing Cu(0) and Cu2O in a different ratio. In the latter case, the resulting composite is in the form of stable nanoroses. When AuCl is added into the resulting solutions of Cu2O@PVP, the partial chemical reduction of AuCl by Cu(0) occurs to form Au(0) and CuCl. At the second step, the electrochemical reduction of AuCl leads to Au/Cu2O@PVP nanocomposite not containing Cu(0), but nanoroses are preserved. Cu2O@PVP nanoparticles are catalytically inactive in the reduction reaction of p-nitrophenol with sodium borohydride in water, and Au/Cu2O@PVP nanocomposites exhibit catalytic activity. In the presence of cetyltrimethylammonium chloride, the catalytic activity of both types of particles sharply increases; in the case of Cu2O@PVP, the increase is so high that the catalytic activity becomes the same as for Au/Cu2O@PVP.

A new family of sterically hindered alkyl(tri-tert-butyl) phosphonium salts (n-CnH2n+1 with n = 2, 4, 6, 8, 10, 12, 14, 16, 18, 20) was synthesized and evaluated as stabilizers for the formation of palladium nanoparticles (PdNPs), and the prepared PdNPs, stabilized by a series of phosphonium salts, were applied as catalysts of the Suzuki cross-coupling reaction. All investigated phosphonium salts were found to be excellent stabilizers of metal nanoparticles of small catalytically active size with a narrow size distribution. In addition, palladium nanoparticles exhibited exceptional stability: the presence of phosphonium salts prevented agglomeration and precipitation during the catalytic reaction.

Pyrazine derivatives Pyrazine derivatives R 0550Fused Nitrogen-Containing Heterocycles. Part 4. 3-Benzoyl-2-oxo-1,2-dihydroquinoxaline Hydrazones and Flavazoles Derived Therefrom. -3-Benzoyl-1,2-dihydroquinoxalin-2-one (I) reacts with hydrazines or thiosemicarbazone to give the corresponding hydrazones [cf. (III), (V)] or thiosemicarbazone (IX), respectively. The hydrazones (III) and (V) undergo intramolecular cyclization in boiling AcOH to furnish pyrazoloquinoxalines (flavazoles) (IV) and (VI), respectively. Formation of a flavazole structure from thiosemicarbazone (IX) is achieved only in the presence of methyl 3-chloro-2-oxo-3-phenylpropionate (X) as a trap of the thiocarbamoyl moiety. -(MAMEDOV, V. A.; KALININ, A. A.; GUBAIDULLIN, A. T.; RIZVANOV, I. K.; CHERNOVA, A. V.; DOROSHKINA, G. M.; LITVINOV, I. A.; LEVIN, Y. A.; Russ.