Viktor P. Krivopalov

Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyrimidine: Synthesis and structure. Catalytic activity of Cu(II) compounds in reaction of ethylene polymerization

The Cu(II) and Cu(I) complexes with 2-(3,5-diphenyl-1H-pyrazole-1-yl)-4,6-diphenylpyrimidine (L) of the composition CuLX2 (X = Cl, Br) and CuL(MeCN)Br are synthesized. According to X-ray diffraction data, the complexes have molecular structures. The molecules L are coordinated to the copper atom in bidentate-cyclic mode, i.e., through the N2 atom of pyrazole and N1 atom of pyrimidine rings. The coordination polyhedron of the Cu2+ ion in CuLX2 compounds is completed to a distorted tetrahedron with halide ions, that of the Cu+ ion in CuL(MeCN)Br compounds, with the bromide ion and the nitrogen atom of acetonitrile molecule. The CuLX2 complexes (X = Cl, Br) in combination with cocatalysts (methylaluminoxane and triisobutylaluminium) exhibit catalytic activity in ethylene polymerization.

Synthesis of 5-nitro-3,4-dihydropyrimidin-2(1H)-ones catalyzed by metal salts. Retro-Henry reaction with formation of N,N′-disubstituted ureas

Three-component condensation of α-nitroacetophenone with aromatic aldehydes and urea in the presence of iron(III), cobalt(II), nickel(II), and copper(II) salts as catalyst led to the formation of 4,6-diaryl-5-nitro-3,4-dihydropyrimidin-2(1H)-ones and N-benzoyl-N′-(1-aryl-2-nitroethyl)ureas. The latter were formed as a result of retro-nitroaldol (retro-Henry) reaction of intermediate 4,6-diaryl-6-hydroxy-5-nitro-3,4,5,6-tetra-hydropyrimidin-2(1H)-ones.

Cu(II) complexes with 4,6-bis(3,5-dimethyl-1H-pyrazole-1-yl)pyrimidine, 4-(3,5-dimethyl-1H-pyrazole-1-yl)-6-(3,5-diphenyl-1H-pyrazole-1-yl)pyrimidine: Synthesis and catalytic activity in ethylene polymerization reaction

The Cu(II) complexes with 4,6-bis(3,5-dimethyl-1H-pyrazole-1-yl)pyrimidine (L1) and 4-(3,5-dimethyl-1H-pyrazole-1-yl)-6-(3,5-diphenyl-1H-pyrazole-1-yl)pyrimidine (L2) of the composition Cu2L1Br4 and Cu2L2A4 (A = Cl, Br), respectively, were synthesized and studied by IR and magnetochemical methods. The molecular structure of the complexes is likely to be binuclear. In the presence of cocatalysts methylaluminoxane and triisobutylaluminium, the title complexes exhibit catalytic activity in the ethylene polymerization reaction.

Complexes of copper(II) and cobalt(II) halides with 4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-methyl-2-phenylpyrimidine: Synthesis, structures, and properties

Copper(II) and cobalt(II) complexes with 4-(3,5-dimethyl-1H-pyrazol-1-yl)-6-methyl-2-phenylpyrimidine (L) of the general formula MLX2 (M = Cu(II), X = Cl and Br; M = Co(II), X = Cl, Br, and I) were obtained. According to X-ray diffraction data, CuLBr2 and CoLX2 (X = Cl, Br, and I) are mononuclear molecular complexes. The ligand L is coordinated to the metal atom in a chelating bidentate fashion through the N atoms of the pyrimidine and pyrazole rings. The coordination polyhedron of the metal atom is extended to a distorted tetrahedron by two halide ions. In solution, CuLBr2 undergoes slow transformation into CuL(1−x)L′xBr2 and the binuclear (X-ray diffraction data) Cu(I) complex [CuL(1−x)L′xBr]2 (L′ is 4-(4-bromo-3,5-dimethyl-1H-pyrazol-1-yl)-6-methyl-2-phenylpyrimidine). The complexes MLX2 show weak antiferromagnetic interactions between the M2+ ions.

Synthesis of substituted 3,4-dihydropyrimidin-2(1H)-ones and pyrimidin-2(1H)-ones by the Biginelli reaction with 3,5-Di-tert-butyl-4-hydroxybenzaldehyde

Three-component acid-catalyzed cyclocondensation of 3,5-di-tret-butyl-4-hydroxybenzaldehyde with urea and ethyl acetoacetate or α-nitroacetophenone (Biginelli reaction) under homogeneous conditions gave the corresponding 5-substituted 3,4-dihydropyrimidin-2(1H)-ones having in position 4 of the heteroring an aryl substituent with sterically shielded hydroxy group. The condensation catalyzed by inorganic salts (Fe3+, Co2+, Zn2+, Li+) was successful only with ethyl acetoacetate as initial methylene-active component. Under analogous conditions, acetophenone and 4-fluoroacetophenone gave rise to 4,6-diarylpyrimidin-2(1H)-ones which are capable of undergoing phenol-quinonemethide tautomerism.

Synthesis and intramolecular conversion of substituted 2-methyl-11-nitro-5,6-dihydro-2H-2,6-methanobenzo[g][1,3,5] oxadiazocin-4(3H)-ones in different solvents

A Biginelli reaction of 5-R-salicylic aldehydes (R = H, Me, Br) with nitroacetone and urea in each case leads to a predominant formation of 2R*,6S*,11S* diastereomers of 8-R-2-methyl-11-nitro-5,6-dihydro-2H-2,6-methanobenzo[g][1,3,5]oxadiazocin-4(3H)-one. In solutions in DMF and DMSO, these diastereomers undergo the oxadiazocine ring opening with setting a three-component equilibrium between predominant 4-(2-hydroxy-5-R-phenyl)-6-methyl5-nitro-3,4-dihydropyrimidin-2(1H)-ones and 2R*,6S*,11S* and 2R*,6S*,11R* diastereomers of methanobenzoxadiazocine as two minor components.

High-spin complex [FeL2(NCS)2]·H2O [L = 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amine]: Synthesis and properties

Complex [FeL2(NCS)2]·H2O (L = 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amine) was prepared as the first example of complex compounds of transition metals with 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amines. The coordination core of the iron atom is a distorted octahedron FeN6. In the range 80–300 K the complex is high-spin, μeff ∼ 5.3 MB. The parameter of the crystal field splitting, 10Dq, for [FeL2(NCS)2]·H2O is ∼10800 cm−1.

Copper(II) complex with 6-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)pyrimidin-4-amine: synthesis, crystal structure, and electronic spectroscopy

A copper(II) complex with 6-(3,5-dimethyl-1H-pyrazol-1-yl)-2-(pyridin-2-yl)pyrimidin-4-amine (L), [CuLCl2], has been synthesized. This compound is formed irrespective of the Cu : L molar ratio (Cu : L = 1 : 1, 2 : 1, and 20 : 1) in the MeOH/H2O/DMF mixture as a single product. ESI-MS data demonstrate that the additional amount of CuCl2 above the Cu : L = 1 : 1 molar ratio, is effectively solvated, and high-nuclearity species are formed in trace amounts in the solution. The complex adopts a distorted square-pyramidal geometry with two chlorides and three nitrogen atoms from L. The electronic spectrum of the complex contains a broad band with a maximum at 12,820 cm−1 within the region characteristic for square-pyramidal chromophores CuA5 (A = Cl, N). Due to Cu ··· Cl contacts, the molecules of [CuLCl2] form the dinuclear [CuLCl2]2 unit. Surprisingly, the NH2-group participates in the formation of NH ··· Cl hydrogen bonds instead of the formation of (NH ··· N3(pyrimidine))2 synthon, which is common for N-heteroaromatic compounds containing the NH2-group in the α-position to aza-atom. These hydrogen bonds together with Cu ··· Cl contacts result in the formation of a 3-D-structure.

2,6-Disubstituted 4-azidopyrimidines: synthesis, kinetic and thermodynamic studies of azide-tetrazole rearrangement by NMR spectroscopy

Thermodynamic and kinetic parameters of the tautomeric tetrazole-azide rearrangement for a series of 2,6-disubstituted 4-azidopyrimidines are determined by NOESY/EXSY and DNMR: ΔH = 15—28 kJ mol–1; ΔS = 47—65 J mol–1 К–1; Еa = 93—117 kJ mol–1; lgA = 15.1—18.9. They are dependent on electronic properties of the substituents and the polarity of solvent.

Synthesis and study of the azide-tetrazole tautomerism in 2-azido-4-(trifluoromethyl)-6-R-pyrimidines (R = H, 4-ClC6H4)

Azide-tetrazole equilibrium in azidopyrimidines bearing trifluoromethyl group on the example of 2-azidopyrimidines has been studied. The latter were synthesized via nitrosation of 2-hydrazino-4-trifluoromethylpyrimidine and reaction of NaN3 with 4-trifluoromethyl-2- chloro-6-(4-chlorophenyl)pyrimidine. The tautomeric equilibrium 5-trifluoro methyl tetrazolo[1,5-a]pyrimidine ⇆ 2-azido-4-trifluoromethylpyrimidine was observed in the absence of solvent and in DMSO-d6 solution, whereas in CDCl3 only an azide form exists. For 2-azido- 4-trifluoromethyl-6-(4-chlorophenyl)pyrimidine, only an azide isomer was detected in CDCl3 solution, and in DMSO-d6 solution it is in equilibrium with 5-(trifluoromethyl)-7-(4-chlorophenyl) tetrazolo[1,5-a]pyrimidine (the tautomer ratio is 99 : 1). Thermodynamic and kinetic parameters of 5-trifluoromethyltetrazolo[1,5-a]pyrimidine ⇆ 2-azido-4-trifluoromethylpyri midine tautomeric rearrangement in DMSO-d6 for 5-trifluoromethyltetrazolo[1,5-a]pyrimidine were determined using the exchange spectroscopy (EXSY) technique.