The acid-catalyzed condensation between 2-aminosubstituted [1,2,4]triazolo[1,5-a]pyrimidines and ... more The acid-catalyzed condensation between 2-aminosubstituted [1,2,4]triazolo[1,5-a]pyrimidines and their analogues with various saturation of the pyrimidine ring and 1,3-diketones or 1,1,3,3-tetramethoxypropane was evaluated as a new approach for the synthesis of diversely substituted polycyclic derivatives of triazolopyrimidine. The reaction of 4,5,6,7-tetrahydro- or aromatic aminotriazolopyrimidines results in selective formation of the corresponding [1,2,4]triazolo[1,5-a:4,3-a']dipyrimidin-5-ium salts, and the condensation of substrates containing the 4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine fragment is accompanied by a cascade rearrangement with unusual recyclization of the dihydropyrimidine ring to yield partially hydrogenated [1,2,4]triazolo[1,5-a:4,3-a']dipyrimidin-5-ium or pyrimido[1',2':1,5][1,2,4]triazolo[3,4-b]quinazolin-5-ium salts. The proposed methodology exhibits a wide scope, providing rapid access to polycondensed derivatives of the [1,2,4]triazolo[1,5-a]pyrimidine scaffold. DFT calculations of the Gibbs free energies of possible isomers were performed to rationalize the experimentally observed reactivity and selectivity.
Acta Crystallographica Section E Structure Reports Online
The asymmetric unit of the title compound, C(14)H(13)O(2)PS(2), contains two crystallographically... more The asymmetric unit of the title compound, C(14)H(13)O(2)PS(2), contains two crystallographically independent mol-ecules, which differ in the conformation of the 1,3,2-benzoxathia-phosphinine moieties (screw boat in the first mol-ecule and envelope in the second mol-ecule). In the crystal, neither classical nor non-classical hydrogen bonds are found. Weak inter-actions (about 2.9-3.0 Å) between the lone pair of the terminal S atoms with H atoms occur. This compound was further characterized by (1)H NMR and IR spectroscopy.
A series of half-sandwich and sandwich-type lanthanide(III) complexes have been prepared using te... more A series of half-sandwich and sandwich-type lanthanide(III) complexes have been prepared using tetrabenzotriazaporphyrin ligands. Reaction of 27-phenyl-29H,31H-tetrabenzo[b,g,l,q][5,10,15]-triazaporphyrin (PhTBTAPH2, 1) with salts [LnX3]·nH2O (Ln = Eu (a), Lu (b); X = OAc, acac) afforded the single- and homoleptic double-deckers (PhTBTAP)LnOAc (2) and (PhTBTAP)2Ln (3) respectively. Heteroleptic double-decker compounds (PhTBTAP)LnPc (4a,b) were obtained upon interaction of 1 with the corresponding Ln mono(phthalocyaninates). An unexpected formation of partially and completely dephenylated co-products 5 and 6 has been detected in the synthesis of sandwich 3, while the possibility of the dearylation of the half-sandwich compound 2 has been demonstrated as well. A more predictable yet firstly observed formation of the triple-decker compound (PhTBTAP)3Eu2 (7) has also been found. Structural studies of 3 supported by 1H NMR spectra, XRD analysis and DFT theoretical calculations reveal that the Eu complex 3a is formed as a single isomer, while the lutetium compound 3b represents an inseparable mixture of two rotational isomers with virtually identical spectral characteristics. The double-decker compounds 3 and 4 reveal intrinsic UV-Vis/NIR absorption as well as peculiar electrochromic behavior. The heteroleptic derivatives 4 generally show intermediate spectral and electrochemical properties with respect to their homoleptic relatives.
Acta crystallographica. Section E, Structure reports online, 2014
The title compound, [Ni(C4H5N4O2)2(H2O)2]·2H2O, represents the first transition metal complex of ... more The title compound, [Ni(C4H5N4O2)2(H2O)2]·2H2O, represents the first transition metal complex of the novel chelating triazole ligand, 2-(5-amino-1H-1,2,4-triazol-3-yl)acetic acid (ATAA), to be structurally characterized. In the mol-ecule of the title complex, the nickel(II) cation is located on an inversion centre and is coordinated by two water mol-ecules in axial positions and two O and two N atoms from two trans-oriented chelating anions of the deprotonated ATAA ligand, forming a slightly distorted octa-hedron. The trans angles of the octa-hedron are all 180° due to the inversion symmetry of the mol-ecule. The cis-angles are in the range 87.25 (8)-92.75 (8)°. The six-membered chelate ring adopts a slightly twisted boat conformation with puckering parameters Q = 0.542 (2) Å, Θ = 88.5 (2) and ϕ = 15.4 (3)°. The mol-ecular conformation is stabilized by intra-molecular N-H⋯O hydrogen bonds between the amino group and the chelating carboxyl-ate O atom of two trans-oriented ligands. In...
A straightforward gram-scale synthesis of 1,3,5,7-tetrakis(methylidene)cyclooctane (TMCO) from co... more A straightforward gram-scale synthesis of 1,3,5,7-tetrakis(methylidene)cyclooctane (TMCO) from commercial adamantane-1,3-dicarboxylic acid has been developed. TMCO exhibits high reactivity toward a number of carbenes and epoxidizing reagents, undergoing multiple cyclopropanations, dihalocyclopropanations, or epoxidations of four double bonds to yield polyspirocyclic products. Stereochemical features of polyspirocyclopropanated compounds have been thoroughly examined in experimental (NMR) and theoretical (DFT) studies. Comprehensive stereochemical assignment of TMCO adducts with dihalocarbenes and spiroepoxy products was achieved. The conditions of the formation of 1-methyl-3,7-bis(methylidene)bicyclo[3.3.1]nonane from the adamantane derivative were optimized, and diadducts of this diene with dihalocarbenes were isolated and characterized.
Kinetic order-disorder phase transitions (space group space group $$ I\bar 4 $$ ↔ space group I41... more Kinetic order-disorder phase transitions (space group space group $$ I\bar 4 $$ ↔ space group I41/a) have been considered for nonactivated and activated scheelite compounds (Na0.5Gd0.5)WO4 (NGW), (Na0.5Gd0.5)MoO4 (NGM), (Na0.5La0.5)WO4(NLW), and (Na0.5La0.5)MoO4 (NLM) synthesized by the Czochralski method and structural and growth sources of crystal dissymmetrization have been suggested. For NGW, it was shown that an increase in the difference between the content of Gd and Na in two positions of the structure with space group $$ I\bar 4 $$ and their ratio leads to an increase in the deviation from centrosymmetry. On the basis of available literature data and our results, it was demonstrated that the degree of order depends on the initial composition of the reaction mixture, crystal growth and cooling rates, activator concentrations, and postgrowth treatment conditions. The inconsistency between X-ray diffraction data and asynchronous second harmonic generation studies was explained by the possibility of formation of centrosymmetric superstructures and/or local ordering of atoms.
The acid-catalyzed condensation between 2-aminosubstituted [1,2,4]triazolo[1,5-a]pyrimidines and ... more The acid-catalyzed condensation between 2-aminosubstituted [1,2,4]triazolo[1,5-a]pyrimidines and their analogues with various saturation of the pyrimidine ring and 1,3-diketones or 1,1,3,3-tetramethoxypropane was evaluated as a new approach for the synthesis of diversely substituted polycyclic derivatives of triazolopyrimidine. The reaction of 4,5,6,7-tetrahydro- or aromatic aminotriazolopyrimidines results in selective formation of the corresponding [1,2,4]triazolo[1,5-a:4,3-a']dipyrimidin-5-ium salts, and the condensation of substrates containing the 4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine fragment is accompanied by a cascade rearrangement with unusual recyclization of the dihydropyrimidine ring to yield partially hydrogenated [1,2,4]triazolo[1,5-a:4,3-a']dipyrimidin-5-ium or pyrimido[1',2':1,5][1,2,4]triazolo[3,4-b]quinazolin-5-ium salts. The proposed methodology exhibits a wide scope, providing rapid access to polycondensed derivatives of the [1,2,4]triazolo[1,5-a]pyrimidine scaffold. DFT calculations of the Gibbs free energies of possible isomers were performed to rationalize the experimentally observed reactivity and selectivity.
Acta Crystallographica Section E Structure Reports Online
The asymmetric unit of the title compound, C(14)H(13)O(2)PS(2), contains two crystallographically... more The asymmetric unit of the title compound, C(14)H(13)O(2)PS(2), contains two crystallographically independent mol-ecules, which differ in the conformation of the 1,3,2-benzoxathia-phosphinine moieties (screw boat in the first mol-ecule and envelope in the second mol-ecule). In the crystal, neither classical nor non-classical hydrogen bonds are found. Weak inter-actions (about 2.9-3.0 Å) between the lone pair of the terminal S atoms with H atoms occur. This compound was further characterized by (1)H NMR and IR spectroscopy.
A series of half-sandwich and sandwich-type lanthanide(III) complexes have been prepared using te... more A series of half-sandwich and sandwich-type lanthanide(III) complexes have been prepared using tetrabenzotriazaporphyrin ligands. Reaction of 27-phenyl-29H,31H-tetrabenzo[b,g,l,q][5,10,15]-triazaporphyrin (PhTBTAPH2, 1) with salts [LnX3]·nH2O (Ln = Eu (a), Lu (b); X = OAc, acac) afforded the single- and homoleptic double-deckers (PhTBTAP)LnOAc (2) and (PhTBTAP)2Ln (3) respectively. Heteroleptic double-decker compounds (PhTBTAP)LnPc (4a,b) were obtained upon interaction of 1 with the corresponding Ln mono(phthalocyaninates). An unexpected formation of partially and completely dephenylated co-products 5 and 6 has been detected in the synthesis of sandwich 3, while the possibility of the dearylation of the half-sandwich compound 2 has been demonstrated as well. A more predictable yet firstly observed formation of the triple-decker compound (PhTBTAP)3Eu2 (7) has also been found. Structural studies of 3 supported by 1H NMR spectra, XRD analysis and DFT theoretical calculations reveal that the Eu complex 3a is formed as a single isomer, while the lutetium compound 3b represents an inseparable mixture of two rotational isomers with virtually identical spectral characteristics. The double-decker compounds 3 and 4 reveal intrinsic UV-Vis/NIR absorption as well as peculiar electrochromic behavior. The heteroleptic derivatives 4 generally show intermediate spectral and electrochemical properties with respect to their homoleptic relatives.
Acta crystallographica. Section E, Structure reports online, 2014
The title compound, [Ni(C4H5N4O2)2(H2O)2]·2H2O, represents the first transition metal complex of ... more The title compound, [Ni(C4H5N4O2)2(H2O)2]·2H2O, represents the first transition metal complex of the novel chelating triazole ligand, 2-(5-amino-1H-1,2,4-triazol-3-yl)acetic acid (ATAA), to be structurally characterized. In the mol-ecule of the title complex, the nickel(II) cation is located on an inversion centre and is coordinated by two water mol-ecules in axial positions and two O and two N atoms from two trans-oriented chelating anions of the deprotonated ATAA ligand, forming a slightly distorted octa-hedron. The trans angles of the octa-hedron are all 180° due to the inversion symmetry of the mol-ecule. The cis-angles are in the range 87.25 (8)-92.75 (8)°. The six-membered chelate ring adopts a slightly twisted boat conformation with puckering parameters Q = 0.542 (2) Å, Θ = 88.5 (2) and ϕ = 15.4 (3)°. The mol-ecular conformation is stabilized by intra-molecular N-H⋯O hydrogen bonds between the amino group and the chelating carboxyl-ate O atom of two trans-oriented ligands. In...
A straightforward gram-scale synthesis of 1,3,5,7-tetrakis(methylidene)cyclooctane (TMCO) from co... more A straightforward gram-scale synthesis of 1,3,5,7-tetrakis(methylidene)cyclooctane (TMCO) from commercial adamantane-1,3-dicarboxylic acid has been developed. TMCO exhibits high reactivity toward a number of carbenes and epoxidizing reagents, undergoing multiple cyclopropanations, dihalocyclopropanations, or epoxidations of four double bonds to yield polyspirocyclic products. Stereochemical features of polyspirocyclopropanated compounds have been thoroughly examined in experimental (NMR) and theoretical (DFT) studies. Comprehensive stereochemical assignment of TMCO adducts with dihalocarbenes and spiroepoxy products was achieved. The conditions of the formation of 1-methyl-3,7-bis(methylidene)bicyclo[3.3.1]nonane from the adamantane derivative were optimized, and diadducts of this diene with dihalocarbenes were isolated and characterized.
Kinetic order-disorder phase transitions (space group space group $$ I\bar 4 $$ ↔ space group I41... more Kinetic order-disorder phase transitions (space group space group $$ I\bar 4 $$ ↔ space group I41/a) have been considered for nonactivated and activated scheelite compounds (Na0.5Gd0.5)WO4 (NGW), (Na0.5Gd0.5)MoO4 (NGM), (Na0.5La0.5)WO4(NLW), and (Na0.5La0.5)MoO4 (NLM) synthesized by the Czochralski method and structural and growth sources of crystal dissymmetrization have been suggested. For NGW, it was shown that an increase in the difference between the content of Gd and Na in two positions of the structure with space group $$ I\bar 4 $$ and their ratio leads to an increase in the deviation from centrosymmetry. On the basis of available literature data and our results, it was demonstrated that the degree of order depends on the initial composition of the reaction mixture, crystal growth and cooling rates, activator concentrations, and postgrowth treatment conditions. The inconsistency between X-ray diffraction data and asynchronous second harmonic generation studies was explained by the possibility of formation of centrosymmetric superstructures and/or local ordering of atoms.
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Papers by Victor Rybakov