First example of the Chan—Lam—Evans N-arylation of bispidines

Russian Chemical Bulletin - The N-arylation of N-Boc-bispidine with arylboronic acids was accomplished under the copper-catalyzed Chan—Lam—Evans reaction conditions. The reaction...     

CaII,YbII and SmII Bis(Amido) Complexes Coordinated by NHC Ligands: Efficient Catalysts for Highly Regio- and Chemoselective Consecutive Hydrophosphinations with PH3

The first example of intermolecular hydrophosphination of styrene, 2-vinylpyridine and phenylacetylene with PH₃ catalyzed by bis-(amido) complexes [(Me₃Si)₂N]₂M(NHC)₂ (M=Ca, Yb, Sm) coordinated by NHC ligands is described. The reactions of styrene with PH₃ proceed under mild conditions in quantitative yields to afford only anti-Markovnikov product and allow for the chemoselective synthesis of primary, secondary and tertiary phosphines. Addition of phenylacetylene to PH₃ regardless the initial molar substrates ratio results in the exclusive formation of a tertiary tris-(Z-styryl)-phosphine. Crucial effect of the Lewis base coordinated to the metal ion in precatalyst on catalytic activity in styrene hydrophosphination with PH₃ was demonstrated. Free NHCs were also found to be able to promote addition of PH₃ to styrene, however they provide much lower reaction rates compared to the metal complexes.     

Diimidazo[4,5-b:4′,5′-e]pyridine: synthesis and nucleophilic aromatic substitution reaction

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New mesomorphic organocyclosiloxanes II. Thermal behaviour and mesophase structure of organocyclohexasiloxanes

Investigations of thermotropic phase transitions performed on organocyclosiloxanes [PhSi(O)OSiR]₆, where R is Me₃, Me₂(CH₂Cl) or Me₂(CH≃CH₂), have revealed that all these hexamers are mesomorphic compounds. The hexamers exhibit uncommon polymesomorphic behaviour forming two quite different mesomorphic structures. The molecular arrangement in the low temperature (LT) modification is characterized by two-dimensional (2D) long-range order with hexagonal packing. The X-ray diffraction pattern and peculiarities of molecular packing in the crystal lead us to suggest that the LT-mesophase is columnar, presumably of the Col_hd type. The LT-mesophase is formed by dimeric moieties, which associate with each other in column-like substructures, the ring planes not orthogonal to the stack axis. The high temperature (HT) mesophase is a plastic crystal (3D-order), where molecules take up positions in a face-centred cubic lattice. This is a very uncommon example of thermal behaviour for plastic crystals that provides a unique opportunity to bridge the gap between plastic crystalline and liquid crystalline mesomorphic behaviour. The thermal and structural properties of the mesophases depend upon the type of side groups of the hexamers. The size of the ring also affects the phase behaviour and the mesomorphic structure. This conclusion is consistent with data obtained by us earlier for cyclotetrasiloxanes.     

Dual-wavelength laser emission from an organic microcavity with terahertz beating

We report on the dynamics of laser emission from an anisotropic organic microcavity filled with the guest-host composite of tris-(8-hydroxy quinoline) aluminium (Alq₃) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM). In a single microcavity, a linesplitting of 0.18 THz between two perpendicularly polarized laser modes is observed. We ascribe this effect to an optical anisotropy in the distributed Bragg reflectors surrounding the organic layer. The temporal behavior of the electromagnetic field is studied by an up-conversion technique and shows an optical beating of 0.18 THz. Two modeling approaches are used to gain insight in the temporal evolution and phase behavior of the two modes. Both point towards the presence of a phase-coupling mechanism in this system. PACS 42.55.Sa     

Synthesis of Naturally Occurring Pyrazine and Imidazole Alkaloids from Botryllus LeachiRID=”a”ID=”a”?Dedicated to Prof. G. M?rkl on the occasion of his 75th birthday

The synthesis of the naturally occurring and biologically active alkaloids 1 and 2, first isolated from the red ascidian Botryllus leachi by Duran et al. [1], is described and the structure proposed for Botryllazine B (1) is confirmed. The analytical data for 2-(p-hydroxybenzoyl)-4-(p-hydroxyphenyl)imidazole (2) are discussed and compared with the literature. With special emphasis of ¹H NMR data the tautomerism of aroylimidazolemethanones is described.     

Synthesis and cascade rearrangement of 3-arylazo-4-(3-ethoxycarbonylureido)furoxans

3-Arylazo-4-(3-ethoxycarbonylureido)furoxans, which were synthesized by the reactions of 4-amino-3-arylazofuroxans with ethoxycarbonyl isocyanate, were subjected to cascade rearrangements under the action of potassium tert-butoxide in dimethylformamide or by heating in dimethyl sulfoxide to form 4-amino-2-aryl-5-nitro-2H-1,2,3-triazoles. X-ray diffraction study and quantum-chemical calculations (B3LYP/6-31G**) of one of ureidofuroxans demonstrated that the intramolecular contact between the carbonyl group and the nitrogen atom of furoxan corresponds to the charge transfer from the lone electron pair of the oxygen atom to the antibonding orbital of the N—O bond.     

Synthesis and structures of 1,1′-bis(diphenylphosphino)metallocenyl complexes M(η 5-C5H4PPh2)2Ru(H2O)2(OTs)2 (M = Fe, Ru, or Os)

The reaction of equimolar amounts of M(η⁵-C₅H₄PPh₂)₂ (M = Fe, Ru, or Os) and [Ru(H₂O)₆](OTs)₂ afforded the M(η⁵-C₅H₄PPh₂)₂Ru(H₂O)₂(OTs)₂ complexes, which were characterized by elemental analysis and ¹H, ¹³C, and ³¹P NMR spectroscopy. The structure of the osmocene complex was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 659—661, April, 2006.