“Four-component” assembly of polyaromatic 4H-cyclopenta[b]thiophene structures based on GaCl3-promoted reaction of styrylmalonates with 5-phenylthiophene-2-carbaldehyde

New “four-component” self-assembly of polyaromatic thiophene structures based on styrylmalonates and 5-phenylthiophene-2-carbaldehyde has been developed. This process is promoted by GaCl₃ and involves two [2?+?3]-annulation steps on the CHO-groups and para-substitution into one Ph-ring. The main feature of discovered process is a high diastereoselectivity with a significant increase in molecular complexity. The resulting polyaromatic structures containing two thiophene moieties in each structure have intense color and strong absorption in a near UV spectral region with absorption maxima in the range of 257–360?nm.     

Reactions of alkyl diazoacetates with pyridinium ylides

Pyridinium (methoxycarbonyl)methylide generated from (methoxycarbonyl)methyl-pyridinium halides under the action of K₂CO₃ reacts with alkyl diazoacetates in CH₂Cl₂ at 20 °C, resulting in the successive addition of three CHCOOMe fragments from the ylide to form 3,6-bis(alkoxycarbonyl)-4,5-diazaoctadienoic acid diesters. Heating of the latter in the presence of pyridine leads to their isomerization to give tetraalkyl tetrahydropyridazine-tetracarboxylates in high yields. Under more drastic conditions (refluxing xylene in the presence of pyridine), the acyclic tetraesters undergo another transformation to form pyrrole-tetracarboxylic acid esters in yields of up to 60%. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 984–988, April, 2005.     

Reactions of diazo esters with electron-deficient alkenes in the presence of Lewis acids

1,3-Dipolar cycloaddition reaction of diazo esters to electron-deficient dipolarophiles to yield the corresponding 1- or 2-pyrazolines was found to be significantly accelerated with Lewis acids (Yb(OTf)₃, Sc(OTf)₃, GaCl₃, EtAlCl₂). The use of GaCl₃ as the catalyst leads to the acceleration not only of the 1,3-dipolar cycloaddition reaction, but also subsequent insertion of the CHCO₂Me electrophilic fragment of methyl diazoacetate into the N-H bond of 2-pyrazolines formed. Such Lewis acids as SnCl₄, BF₃, TiCl₄, and In(OTf)₃ are not efficient in the described processes, since they rapidly decompose starting diazo compounds.     

Synthesis and spectroscopic study of hexadecaalkyl-substituted rare-earth diphthalocyanines

New hexadecaalkyl-substituted diphthalocyanine complexes of lanthanides ^RPc₂Ln (R = Et, or Bu; Ln = Lu, Dy, or Eu) were synthesized by three methods: in solution in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, in a melt of a mixture of the reagents, and under microwave irradiation. The first of the above-mentioned procedures has an advantage for the preparation of Dy and Eu diphthalocyanines, whereas the melt synthesis is a method of choice for the preparation of Lu complexes. The reaction time decreases in going from the first to the third method. The structures of the complexes were confirmed by mass spectrometry, NMR spectroscopy, and electronic absorption spectroscopy.     

Unusual formation of hydroperoxides in the reactions of substituted spiro[pyrazolinecyclopropanes]

3-Cyano- and 3-(alkoxycarbonyl)spiro[2-pyrazoline-5,1’-cyclopropane] and 5-phenylspiro[1-pyrazoline-3,1’-cyclopropane] undergo unusual transformations into 3(5)-substituted 5(3)-(2-hydroperoxyethyl)pyrazoles in the presence of atmospheric oxygen. The conditions for the formation of hydroperoxides (e.g., in oxygen-saturated solutions of spiro[2-pyrazoline-5,1’-cyclopropanes] in CHCl₃) and their conversion into (2-hydroxyethyl)pyrazoles or the corresponding nitrates under the action of nitrosating reagents were considered.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2160–2164, October, 2004.     

Stability of Phosphorus Trihalide Solutions Used in Polarography

The behavior of PCl₃ and PI₃ solutions in acetonitrile containing no more than 0.02 wt % H₂O in storage at room temperature was studied.     

Electrode Reactions Involving Arsenic and Its Inorganic Compounds

The available information on the electrochemical properties of arsenic and its inorganic compounds is generalized. Processes of practical value are considered. These include the formation of free arsenic from solutions as a solid phase in the form of powder or galvanic coatings; the synthesis of arsine, arsenic acid, and arsenates; and use of electrochemical techniques for the waste water purification.