Application of the Thorpe—Ziegler reaction for the synthesis of functionalized thiophenes,thienopyrimidines, and thienotriazines

Approaches to the synthesis of 3-aminothiophene-2,4-dicarboxylic acid derivatives and to their conversions into thieno[3,4-d]pyrimidines, thieno[3,4-d]-1,2,3-triazines, and thieno[3,2-d]pyrimidines are developed.     

Quantum oscillations of shubnikov-de Haas transverse kinetic coefficients

Shubnikovde Haas oscillations of the transverse magnetoresistance and of the Hall effect are analyzed. The magnetic field dependence of the monotonic components of the transverse magnetoresistance and conductivity are determined. It is found that these dependences do not follow the saturation law usually assumed to hold in a strong magnetic field. It is shown that the reason is the magnetic field dependence of the Hall angle and of the carrier effective mass.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 60–65, May, 1979.The author is grateful to Yu. A. Bykovskii, under whose guidance the experiments were performed, to V. F. Elesin for indicating the present problem, and to L. G. Iofee for help in handling the experimental results.     

Photogalvanic effect in an asymmetric system of three quantum wells in a strong magnetic field

The photogalvanic effect (PGE) in an asymmetric undoped system of three GaAs/AlGaAs quantum wells illuminated with white light of various intensities is investigated in magnetic fields up to 75 kOe at temperatures ranging from 4.2 K up to 300 K. A maximum of the spontaneous photogalvanic current J ^PGE as a function of the magnetic field predicted by A. A. Gorbatsevich et al., JETP Lett. 57, 580 (1993), is observed. Analysis of the experimental data shows that the main initial characteristic of the PGE is not the spontaneous current but rather the electromotive force E ^PGE arising in the direction perpendicular to the applied magnetic field. It is determined that this emf is independent of the intensity of the incident light, increases linearly with the size d of the illuminated region, and decreases slowly with temperature: E _max ^PGE ∼0.8 V at 300 K and ∼0.1 V at 4.2 K for d∼3 mm. The curve E ^PGE(H) at room temperature is determined with allowance for the strong transverse magnetoresistance of the nanostructure. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 3, 197–202 (10 February 1996)     

Determination of the electron temperature of a degenerate semiconductor in quantizing fields under heating by an electric field

Investigations of the Shubnikov-de Haas oscillation of the transverse magnetoresistance due to the magnitude of the electric field in n-type InSb with 5 · 10¹⁵, 3 · 10¹⁶ cm^–3 concentrations at a 4.2 °K temperature are carried out herein. A method is proposed to determine the electron temperature T_e; dependences of T_e on the electric and magnetic fields in the sample are obtained for a transversely oriented magnetic field. The relaxation time of the electron energy is estimated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 96–100, February, 1972.     

Energy spectrum of a GaAs (δ-Sn) structure on a vicinal face

The potential profile, electron energy levels, and corresponding wave functions are calculated for a gallium-arsenide structure with a δ-doped tin vicinal face GaAs(0.3°, δ-Sn). Calculated values of the electron densities in the subbands agree well with the quantities obtained from an analysis of the Shubnikov-de Haas oscillations and photoluminescence spectra of the structure. On the basis of the calculated band diagram the lines observed in the photoluminescence spectrum of the GaAs(0.3°, δ-Sn) structure are identified here for the first time as associated with electron transitions on the size-quantization levels in the tin δ-layer. Fiz. Tverd. Tela (St. Petersburg) 39, 1853–1856 (October 1997)     

Synthesis of thieno[3,4-d]pyrimidines by the reactions of 3-amino-4-carbamoylthiophene derivatives with 1,3-dicarbonyl compounds

The reactions of ethyl 3-amino-4-carbamoyl-5-methylthiophene-2-carboxylate with 1,3-dicarbonyl compounds were studied. During the reactions, the corresponding ketone is eliminated to give ethyl 5-methyl-4-oxo-3,4-dihydrothieno[3,4-d]pyrimidine-7-carboxylates.     

Synthesis and Study of the Properties of 7,8-Polymethyleneimidazo[4,5-d]-1,3,2-diazaphosphorin-2-thiones

In thionation of cyclic N-cyanoamidines, a four-step process occurs that leads to derivatives of novel heterocyclic systems: 7,8-polymethyleneimidazo[4,5-d]-1,3,2-diazaphosphorin-2-thiones. We have studied the chemical and spectral properties of the compounds obtained.     

Acetals of lactams and acid amides. 54. New synthesis of pyrimido[4,5-f]pyrrolizines

A synthesis of pyrimido[4,5-f]pyrrolizine derivatives has been carried out, which is based on the intramolecular cyclization of 7-functionally substituted 6-amino-pyrrolizines with the participation of substituents in the 6- and 7-positions.For communication 53, see [1],Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 830–832, June, 1989.     

Lactam and acid amide acetals 68. 1-Cyanomethyl-2-pyrrolidone diethylacetal in the synthesis of 7,8-trimethylenepurine derivatives

1-Cyanomethyl-2-cyaniminopyrrolidine was synthesized by the reaction of 1-cyanomethyl-2-pyrrolidone diethylacetal with cyanamide. The product undergoes Thorpe—Ziegler cyclization under the influence of sodium ethoxide to give 2-amino-3-cyano-5,6-dihydro-7H-pyrrolo[1,2-a]imidazole, from which 4-amino derivatives of pyrrolo[2,1-f]purine were synthesized.See [1] for Communication 67.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 754–758, June, 1991.