The Chemistry of Carbenoids and Other Thermolabile Organolithium Compounds

Organolithium compounds are thermally quite stable, despite their extremely high reactivity. Thermolability, i.e. the property of undergoing irreversible changes at low temperatures without the participation of molecules of a different kind, is associated with additional functional groups, which may be readily eliminated together with the metal cation, may cause intramolecular rearrangements, or may lead to intermolecular additions and substitutions involving several molecules of the same type. Thermolabile organolithium compounds have frequently been postulated or detected as intermediates of important reactions, and are therefore of theoretical and practical interest. If certain precautions are taken, it is occasionally possible (mainly at low temperatures) to prepare them intact, and hence to release them from the constraint of the fate assigned to them as short-lived intermediates. Investigations with this aim have for some time occupied a place of considerable importance in the chemistry of organometallic compounds.     

2H/1H Isotope Shifts for 6Li-NMR: First Experimental Detection and Applications to Structural Problems in the Field of Organolithium Compounds

Deuterium-induced isotope effects on ⁶Li chemical shifts, transmitted over two bonds, ²Δ(⁶Li)(²H/¹H), have been measured for the first time for methyllithium and the system methyllithium/lithium iodide. The observed shifts are to low field and range from 15 to 20 ppb per CD₃ group. The multiplicity and intensity distribution of the ⁶Li signals resulting for mixtures of CH₃- and CD₃-containing samples in the limit of slow inter- as well as intra-aggregate exchange yield information about the size of the various clusters present in diethylether solution. It is expected that these isotope shifts can facilitate structural investigations of organolithium compounds. In some cases, the results of such measurements are expected to be less ambiguous then the conclusions based on multiplets that arise from scalar ¹³C,⁶Li spin-spin coupling.     

Investigation of microstructure of glycidyl methacrylate/α-methyl styrene copolymers by 1D- and 2D-NMR spectroscopy

The copolymers of glycidyl methacrylate/α-methyl styrene were synthesized. The quantitative ¹³C{¹H}-NMR spectroscopy was used to determine the copolymer compositions. The distortionless enhancement by polarization transfer, ¹³C-¹H heteronuclear single quantum coherence and total correlation spectroscopy were used for the complete spectral assignment of ¹³C{¹H}- and ¹H-NMR spectra.     

Neue Vertreter der Li8SnO6-Familie: Li8IrO6, Li8PtO6 und Li8CeO6 [1, 2]

New Compounds of the Li₈SnO₆-Type: Li₈IrO₆, Li₈PtO₆, and Li₈CeO₆ For the first time single crystals of Li₈IrO₆ (dark-violet, a = 541.51, c = 1505.84 pm), Li₈PtO₆ (transparent/greenish yellow, a = 541.46, c = 1501.43 pm), and Li₈CeO₆ (transparent/colourless, a = 564.30, c = 1602.71 pm) have been prepared and investigated by x-ray. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Ionic Radii, MEFIR, are calculated and discussed.     

A New and Efficient Synthesis of 2H-3, 1-Benzoxazine Compounds

2H-3, 1-Benzoxazine heterocyclic compounds are a series of potent nonsteroidal pro- gesterone receptor agonists1-3 and have many other applications such as carbonaceous electrode, plant growth regulating and anti-stress activities4-6, etc.. Comparing to other benzoxazine series, such as 1, 4-benzoxazine, 2H-1, 3-benzoxazine, etc., little attentions have been paid for this series of compounds. There is only one method for the preparation of 2H-3, 1-benzoxazine, e.g. cyclocondensation of o-amin…     

[1,2]-Wittig Rearrangement of Acetals III [1]. New 1,2-Alkoxyalcohols, 1,2-Alkoxyaminesand 1,2-Dialkoxy Compounds as Chiral Ligands for Organomagnesium and Organolithium Compounds and forLithium Aluminum Hydride

 Eight O-substituted 1,2-diols and one O,N-substituted 1,2-aminoalcohol derived from 2-alkoxyoctahydro-7,8,8-trimethyl-4,7-methanobenzofurans via a [1,2]-Witting rearrangement and subsequent substitution were synthesized and tested as additives for the enantioselective addition of butyllithium and butylmagnesium chloride to benzaldehyde and for the reduction of acetophenone with lithium aluminum hydride. The selectivity of the reactions was determined by GC of the obtained 1-phenyl-1-pentanol and 1-phenylethanol on a chiral phase. Best results with regard to selectivity (52% ee and 94% ee, resp.) were achieved in the formation of 1-phenyl-1-pentanol by addition of the substituted 1,2-aminoalcohol to the organometallic reagent and in the reduction of acetophenone using an α-alkoxyalcohol (62%ee).     

Synthesis of D-(6R) - and D-(6S) -(6-2H1) glucose

Chemical synthesis ofD-(6R)- and D(6S)-(6-²H₁) glucose is described comprising (i) formation of 6-²H₁)-3-o-benzyl-5,6-dideoxy-l, 2-0-isopropylidene-α-D-xylo-hex-5-ynofuranose from D-glucose; (ii) stereospecific reduction of the deuterated acetylene functionality to (E)- or (Z)-deuterated olefin; (iii) stereospecific cis-dihydroxylation of the deuterated olefin; and (iv) separation of stereoisomers based on the intrinsic chirality of D-glucose and subsequent deprotection.     

[1,2]-Wittig Rearrangement of Acetals III [1]. New 1,2-Alkoxyalcohols, 1,2-Alkoxyaminesand 1,2-Dialkoxy Compounds as Chiral Ligands for Organomagnesium and Organolithium Compounds and forLithium Aluminum Hydride

Summary.  Eight O-substituted 1,2-diols and one O,N-substituted 1,2-aminoalcohol derived from 2-alkoxyoctahydro-7,8,8-trimethyl-4,7-methanobenzofurans via a [1,2]-Witting rearrangement and subsequent substitution were synthesized and tested as additives for the enantioselective addition of butyllithium and butylmagnesium chloride to benzaldehyde and for the reduction of acetophenone with lithium aluminum hydride. The selectivity of the reactions was determined by GC of the obtained 1-phenyl-1-pentanol and 1-phenylethanol on a chiral phase. Best results with regard to selectivity (52% ee and 94% ee, resp.) were achieved in the formation of 1-phenyl-1-pentanol by addition of the substituted 1,2-aminoalcohol to the organometallic reagent and in the reduction of acetophenone using an α-alkoxyalcohol (62%ee). Received March 10, 2000. Accepted March 23, 2000     

Studies on ABX6 Compounds. IV. The structures of AUI6 compounds (A: Sr,Eu, Ba)

The compounds SrUI₆, EuUI₆ and BaUl₆ are synthesized for the first time. Their crystal structures are isotypic, and they can be described as ordered substitution variants of the AlCl₃ type.     

1,3-Anionic Cycloadditions of Organolithium Compounds: An Initial Survey. New synthetic methods (4)

In the field of [3 + 2]-cycloaddition reactions, 1,3-anionic cycloadditions have now joined 1,3-dipolar cycloadditions as a second reaction type of major general importance. The cycloaddition in question has been found to occur with 2-azaallyllithium compounds, allyllithium compounds (with an electron acceptor located on C²), and 1,3-diphenylpropargyllithium. Compounds with CC, CN, NN, and CS double bonds and those with CC and CN triple bonds were found to be 1,3-anionophilic. 1,3-Anionic cycloaddition opens new routes to 1-aza-, 1,2-diaza-, 1,3-diaza-, 1,2,4-triaza-, and 1-thia-3-azacyclopentane derivatives, to pyrroles and imidazoles, as well as (and this appears to be of special importance) to cyclopentane derivatives. Currently available data attribute stereospecificity to the 1,3-anionic cycloadditions, which occupy an interesting intermediate position between 1,3-dipolar cycloadditions and transition-metal-catalyzed cyclizations. A two-step mechanism has been demonstrated in one case.     

Compounds of 6Li and natural Li for EPR dosimetry in photon/neutron mixed radiation fields

Formates and dithionates of 6Li, enriched and 7Li in natural composition of Li offer a possibility to measure the absorbed dose from photons and thermal neutrons in a mixed radiation field for instance at a boron neutron capture therapy (BNCT) facility. Tests with formates and dithionates of enriched 6Li and lithium compounds with natural composition have been performed at the BNCT facility at Studsvik, Sweden. Irradiations have been performed at 3 cm depth in a Perspex phantom in a fluence rate of thermal neutrons 1.8 x 10(9) n cm(-2) s(-1). The compounds were also irradiated in a pure X-ray field from a 4MV linear accelerator at 5 cm depth in a phantom with accurately determined absorbed doses. The signal intensity and shape was investigated within 3 h after the irradiation. A single line spectrum attributed to the CO2- radical was observed after irradiation of lithium formate. An increase in line width occurring after neutron irradiation in comparison with photon irradiation of the 6Li sample was attributed to dipolar broadening between CO2- radicals trapped in the tracks of the alpha particles. A spectrum due to the SO3- radical anion was observed after irradiation of lithium dithionate. The signal amplitude increased using the 6Li in place of the Li with natural composition of isotopes, in studies with low energy X-ray irradiation. Due to the decreased line width, caused by the difference in g(N) and I between the isotopes, the sensitivity with 6Li dithionate may be enhanced by an order of magnitude compared to alanine dosimetry. After comprehensive examination of the different combinations of compounds with different amounts of 6Li and 7Li regarding dosimetry, radiation chemistry and EPR properties these dosimeter material might be used for dose determinations at BNCT treatments and for biomedical experiments. Interesting properties of the radical formation might be visible due to the large difference in ionization density of neutrons compared to photons.     

新型1,2,4-三唑类化合物的合成及生物活性研究

本文利用2-吡啶醛或4-吡啶醛与1-(1H-1.2.4-三唑-1-基)酮发生羟醛缩合反应,合成了一类新型的三唑类化合物3和4,其结构经元素分析、¹HNMR和IR及MS所确证.通过生物活性测试结果表明,目标化合物具有很好的杀菌活性,同时也有较好的除草活性和植物生长调节活性.     

Determination of Melting Points for A2B6 Compounds

A new technique of rapid heating, recording both the melting and evaporation processes in an open system was proposed to determine the melting points of A2B6 (A=Zn, Cd) compounds. The different melting character and temperatures were detected for the equiatomic and non-stoichiometric composition of A2B6. A fit of these data to previously obtained results was considered and the reasons for their discrepancy were discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

1-(2,4-二氯苯基)-1-氨基-4,4-二甲基-2-(1,2,4-三唑-1-基)-3-戊酮(醇)的合成及生物活性研究

通过不同的胺对烯唑醇前体1的1,4-亲核加成反应,合成了目标化合物2,并将其还原得到了其还原产物3.生物活性测试结果发现,化合物3表现出较好的杀菌活性及一定程度的植物生长调节活性.     

New layered compounds with honeycomb ordering: Li3Ni2BiO6, Li3NiM'BiO6 (M' = Mg, Cu, Zn), and the delafossite Ag3Ni2BiO6

The new layered compound Li(3)Ni(2)BiO(6) has been prepared by a solid-state reaction. It crystallizes in the monoclinic C2/m space group; its lamellar structure is characterized by a honeycomb ordering between Ni(2+) and Bi(5+) within the slabs, while Li(+) ions occupy octahedral sites in the interslab space. Stacking defects weakly alter the XRD pattern. By substitution of half of the nickel ions, the new phases Li(3)NiM'BiO(6) (M' = Mg, Cu, Zn) isostructural with Li(3)Ni(2)BiO(6) have been synthesized under similar conditions. All these compounds demonstrate paramagnetic behavior at high temperature, and Li(3)Ni(2)BiO(6) exhibits an antiferromagnetic ordering at 5.5 K. By topotactic molten salt ionic exchange, the new delafossite compound Ag(3)Ni(2)BiO(6) has been also obtained and characterized.