Catalytic Hydrosilylation of Furan, Thiophene, and Pyridine Aldimines

The addition of hydrosilanes (HSiEt₃, HSiMe₂Ph, H₂SiPh₂) to the CH=N bond of heterocyclic azomethines has been studied in the presence of monovalent complexes of rhodium and palladium. The effect on the reaction of the CF₃ group of the aldimines, which were obtained from O-, S-, and N-heteroaromatic aldehydes and 2-trifluoromethylaniline, has been clarified, as were other regularities of the processes being studied. A series of corresponding furans, thiophenes, and pyridine amines has been synthesized.     

A new method for the synthesis of silicon-and germanium-containing 2-acetylfurans and 2-acetylthiophenes

A new method was developed for the synthesis of silicon-and germanium-containing acetylfurans and acetylthiophene by metallation of 2-acetylfuran or 2-acetylthiophene with n-BuLi at low temperature after protection of the carbonyl group with lithium N-methylpiperazide and reaction of the lithium derivative with various trialkyl-, alkylphenyl-, and cycloalkylchlorosilanes or trialkylchloro(bromo)germanes. The cytotoxic activity of the new compounds was studied, and it was established that the silicon-and germanium-containing acetylfurans and acetylthiophenes are substances with low toxicity (LD₅₀ 312->2000 mg/kg) and have low cytotoxicity toward HT-1080 and MG-22A tumor cells. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 192–199, February, 2007.     

Synthesis of N-Pyridylmethylidene-2-aminopyridines and their Methyl-substituted Derivatives in the Presence of Molecular Sieves

We have studied condensation of 2-, 3-, 4-pyridinealdehydes and 6-methylpyridine-2-aldehyde with 2-aminopyridine and its 3-, 4-, and 6-methyl derivatives in benzene in the presence of molecular sieves. The reactions occur even at room temperature to form the corresponding pyridyl-pyridyl azomethines, and also aminals. We have determined the optimal conditions for carrying out the processes with the aim of obtaining both types of products. We consider the characteristics of the mass spectra for the synthesized aldimines. We present the X-ray diffraction results for the two aminals.     

Novel Stereoselective Phase Transfer Catalytic Synthesis and Some Applications of ( E )-2-Chlorovinylthioarenes and Hetarenes

A novel two-step method for the preparation of ( E )-2-chlorovinylthioarenes (or hetarenes) from thiols and 1,1,2-trichloroethane in the phase transfer catalytic systems solid K 2 CO 3 /solid KI/18-crown-6/xylene and solid KOH/18-crown-6/toluene has been developed. ( E )-2-chlorovinylthioarenes were isolated in yields up to 98%. Utilization of ( E )-2-chlorovinylthioarenes in the Heck and Stille reactions has been shown.     

Synthesis of 2-(pyridylazo)-2-furyl-and 2-(pyridylazo)-2-thienylmethines and other heterocyclic Schiff bases in the presence of molecular sieves

The reactions of 2-furaldehyde, 2-thiophenecarbaldehyde, and their 5-methyl derivatives with 2-aminopyridines and some other amines in the presence of molecular sieves as a dehydrating agent and acid catalyst have been studied. A series of new heterocyclic azomethines was synthesized. Proposals were made for the mechanism of the condensation involving 2-aminopyridines and the structure of the intermediates in these processes.Latvian Institute of Organic Synthesis, Riga LV-1006, Latvia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 890–897, July, 2000.     

Electrochemical hydrogen storage and usage aspects: Nickel electrode in acidic electrolyte

The conditions of electrochemical formation of nickel hydride are investigated. The electrochemical properties of different nickel-based materials (bulk, porous, foamed tapes) are examined to state the hydrogen adsorption/absorption phenomena and possibility to use them as a negative electrode in hydrogen devices (electrolyzers, rechargeable batteries, fuel cells). Surface activation of nickel materials are made by electroplating and etching methods. Thin palladium coating is used to prove the formation of nickel hydride during cathodic charging. Volt-amperometric and kinetic measurements show that not only palladium, but also activated nickel plays important role in the surface activation of electrode materials and promotion of hydrogen absorption in nickel substrate materials. Published in Russian in Elektrokhimiya, 2007, vol. 43, No. 5, pp. 624–629. Based on the paper delivered at the 8th Meeting “Fundamental Problems of Solid-State Ionics, Chernogolovka (Russia), 2006. The text was submitted by the authors in English.     

Mass spectra of heteroaromatic derivatives of silicon,germanium, and tin (review)

A review summarizing material on the mass spectrometry of furyl and thienyl derivatives of the Group IVB elements.Dedicated to Professor A. R. Katritsky in connection with his 65th birthday.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, 891–898, July, 1993.     

Electrochemical oxidation of 4-monoalkyl-substituted 1,4-dihydropyridines

The electrochemical oxidation of 4-monoalkyl-substituted 1,4-dihydropyridines has been studied in an aprotic medium and in the presence of pyridine. In an aprotic medium the products of oxidation are both 4-alkyl-substituted and 4-unsubstituted pyridines or mixtures of them. On oxidation in acetonitrile of 4-Et-, 4-n-Pr-, and 4-i-Bu-substituted dihydropyridines, 2-methylene-1,2,3,4-tetrahydropyridines were obtained in addition to the oxidized forms. In the presence of base the products of preparative electrolysis of the studied compounds were 4-alkyl-substituted pyridines. The exception was the 4-i-Pr- substituted dihydropyridine which was dealkylated on oxidation even in the presence of base. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1829–1838, December 2008.     

Recyclization of 2-amino-4,4-dimethyl-Δ2-1,3,4-thiadiazolin-4-io-5-acetates into 2-dimethyl-hydrazono-2,3-dihydro-4h-1,3-thiazin-4-ones

2-Amino-4,4-dimethyl- ²-1,3,4-thiadiazolinio-5-acetates were found to recyclize into 2-dimethylhydrazono-2,3-dihydro-4H-1,3-thiazin-4-ones. The similar mass fragmentation of these compounds is explained by the occurrence of a rearrangement under electron impact which is analogous to the chemical recyclization thiadiazolinioacetates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1680–1684, 1992.