Enantioselective Diels-Alder reactions of α-fluorinated α,β-unsaturated carbonyl compounds : Part 5. Chemical consequences of fluorine substitution

α-Fluoro-α,β-unsaturated carbonyl compounds, compared with the corresponding non-fluorinated parent compounds, are less reactive in Diels-Alder reactions with normal 1,3-dienes. The cycloadducts of such dienophiles with 2,3-dimethylbutadiene (1) or o-quinodimethane (6) exhibit low stability whereas the corresponding cycloaddducts formed with cyclopentadiene (7) are stable compounds. While the cycloadditions of oct-1-en-3-one (2e) or benzyl acrylate (10b) with 7 are endo-selective, the corresponding reactions with 2-fluorooct-1-en-3-one (2a) or benzyl 2-fluoroacrylate (10a) are exo-selective. Applying Lewis acids as mediators, the reactions with non-fluorinated dienophiles become even more endo-selective, while the corresponding reactions with the fluorinated analogues become more exo-selective. Using enantiopure Lewis acidic metal complexes such as titanium TADDOLates, low enantioselectivity is observed in reactions of 7 with 2e or 10b. Moderate enantioselectivity (max. 43% enantiomeric excesses (ee)) is found in the corresponding cycloadditions of 7 with 2a, whereas 10a shows practically no enantioselectivity. The more efficient chiral induction in reactions with the fluorinated dienophile 2a might be caused by a chelate-like complexation of the carbonyl compound involving the fluorine substituent.     

手性双唑啉铜配合物在不对称合成中的应用

综述了手性双E唑啉配体的主要结构类型,并讨论了手性双E唑啉铜配合物在不对称Diels-Alder反应、Ene反应、Mukaiyama adol反应、烯丙基氧化、环丙烷化、氮杂环丙烷化等反应中的应用。     

Tricarbonylchromium complexes with phenalene. Synthesis, structure, and thermal rearrangements

The reaction of phenalene with Cr(CO)₃Py₃/BF₃·OEt₂ afforded a mixture of two isomeric complexes, tricarbonyl(6a,7-9,9a,9b-·⁶-phenalene)chromium (1) and tricarbonyl(3a,6a,9b,4-6-·⁶-phenalene)chromium (2). Deprotonation of the mixture of compounds1 and2 followed by treatment with MeI, BuⁿI, or D₂O gave complexesexo-1-R-1 (3–5: R=Me (3), Buⁿ (4), or D (5)). The molecular geometry of complex3 was established by X-ray structural analysis. Heating of complex5 in toluene or C₆F₆ at 90–110 °C resulted in redistribution of deuterium among positionsexo-1,endo-1, and 3 in the resulting complexes of types1 and2 via sigmatropic shifts of the H _exo and H _endo atoms in the nonaromatic ring as well asvia inter-ring migrations of the tricarbonylchromium group. In the case of3, the methyl label is distributed among positionsexo-1 and3 to form isomeric complexes with similar structures (exo-1-Me-2 (6), 3-Me-2 (7), and 3-Me-1 (8), respectively)via processes analogous to those observed in the case of isomerization of compound5 (except for migration of the H _exo atom). The mechanisms of these rearrangements are discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1863–1880, October, 1997.     

Synthesis,crystal structures,and redox behavior of bis(2-phenylindenyl) nickel and bis(2-phenylindenyl)zirconium dichloride

Redox reactions of the sandwich jn⁵-(Ph)Ind]₂Ni complex (1) (where (Ph)Ind is the 2-plrenylindenyl anion) in CH₂CI₂ and of the bent-sandwich (⁵-(Plr)Ind]₂ZrCl₂ complex (2) in THF have been studied by low-temperature cyclic voltammetry. Complex ( undergoes quasi-reversible two-step oxidation to cation i+ and dication 12+, which are stable at room temperature within the cyclic voltammetry time scale. Two-electron reduction of complex 1 is irreversible up to -50 °C, and this process is accompanied by destruction of the sandwich structure of the complex. Redaction of complex 2 is described by the conventional scheme for bent-sandwich complexes. According to this scheme, further one-electron reduction of radical anion 2- generates dianion 2^2–, which eliminates two CI^– ions to afford bisindcnyl sandwich complex (⁵-(Ph)lnd]₂Zr (3). This complex is stable at T < -45 °C within the cyclic voltammetry time scale and is capable of undergoing one-electron reduction to the corresponding radical anion 3-. Synthesis and crystal structures of complexes 1 and 2 are reported.Translated fromIzvestiya Akademii Nauk. Seriya Kidmicheskaya, No. 6, pp. 1529–1536, June, 1996.     

Synthesis and crystal structure of the deuterated organic conductor, (d8-ET)4[Hg2(SCN)4Cl2]

On the basis of completely deuterated bis(ethylenedithio)tetrathiafulvalene (d₈-ET), new organic conductors, (d₈-ET)₄[Hg₂(SCN)₄Cl₂] and (d₈-ET)₂[Hg(SCN)₂Br] have been synthesized and studied by X-ray structural analysis. Unlike nondeuterated organic metalsk-(ET)₂[Hg(SCN)_3–n X _n ] (X = Cl or Br;n=1 and 2), the crystal structure of (d₈-ET)₄[Hg₂(SCN)₄Cl₄] exhibits -type packing of the d₈-ET radical cations in the conducting layer and a polymeric structure of anions, in which both the SCN groups and the Cl atoms are involved in the bridging bonds. The crystals of (d₈-ET)₂[Hg(SCN)₂Br] and the nondeuterated form (ET)₂[Hg(SCN)₂Br] are isostructural.Translated fromIzvestiya Akademii Nauk. Seriya Khlmicheskaya, No. 5, pp. 905–909, May, 1995.This work was financially supported by the International Science Foundation (Grant RE1 000), the Scientific Council on the Problems of High-Temperature Superconductivity (Project No. 93030), and the Russian Foundation for Basic Research (Project No. 94-03-09950).     

3,6-Di-tert-butyl-o-benzosemiquinone complexes of copper(1) with bidentate bis(diphenylphosphine) ligands. Synthesis, structures, and properties

New mononuclear 3,6-di-tert-butyl-o-benzosemiquinone complexes of copper(1) with bis(diphenylphosphine) ligands were synthesized: (DBSQ)Cu(dppe) (1) (DBSQ=3,6-di-tert-butyl-o-benzosemiquinone and dppe=1,2-bis(diphenylphosphino)ethane), (DBSQ)Cu(dppp) (2) (dppp=1,3-bis(diphenylphosphino)propane), (DBSQ)Cu(dppn) (3) (dppn=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl), and (DBSQ)Cu(dppfc) (4) (dppfc=1,1′-bis(diphenylphosphino)ferrocene). The compositions and structures of complexes1–4 were characterized by elemental analysis and electronic absorption, IR, and ESR spectroscopy. The molecular structures of complexes3 and4 were established by X-ray diffraction analysis. The reactions of elimination and replacement of neutral ligands in the coordination sphere of the complexes were studied by ESR spectroscopy. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2333–2340, November, 1998.     

Synthesis, molecular and crystal structure, and features of the electronic structure of bis(O’i)-chelated bis(2,2-dimethylbenzo-[2H]-4-oxo-1,3-oxazino-3-methyl)difluorosilane

A method has been developed for the synthesis of a bis(O→Si)-chelated bis(2,2-dimethylbenzo[2H]-4-oxo-1,3-oxazino-3-methyl)difluorosilane from 2,2-dimethyl-3-trimethylsilylbenzo[2H]-1,3-oxazin-4-one and bis(chloromethyl)dichlorosilane via the intermediate formation of the corresponding unstable bis-chelated dichloride, subsequent hydrolysis with NaHCO₃ and, without separation, treatment of the hydrolysis product with boron trifluoride etherate. Analysis of the electron density distribution showed the presence of dative bonding in both O→Si-F fragments. Dedicated to Prof. Edmunds Lukevics on the occasion of his 70th birthday __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1866–1879, December, 2006.     

Synthesis,spectral characterization,electrochemical studies and catalytic properties in Suzuki–Miyaura coupling reactions of the mononuclear PdII,trinuclear PdII(BPh2)2 and RuII?PdII?RuII type complexes containing 4‐amino‐1‐benzyl piperidine and phenyl groups

The ligand containing the 4‐amino‐1‐benzyl piperidine group, N, N′‐(4‐amino‐1‐benzyl piperidine)‐glyoxime, (LH₂) (1) was prepared from 4‐amino‐1‐benzyl piperidine with anti‐dichloroglyoxime at ? 15 °C in absolute Tetrahydrofuran (THF). In the trinuclear [Pd(L)₂Ru₂(phen)₄](ClO₄)₂ (4) and [Pd(L)₂Ru₂(bpy)₄](ClO₄)₂ (5) metal complexes, the Pd^II ion centered into the main oxime core by the coordination of the imino groups while the two Ru^II ions coordinated dianionic oxygen donors of the oxime groups and linked to the ligands of 1,10‐phenanthroline and 2,2′‐bipyridine. The mono and trinuclear metal complexes were characterized by elemental analyses, FT‐IR, UV–vis, ¹H and ¹³C‐NMR spectra, magnetic susceptibility measurements, molar conductivity, cyclic voltammetry, mass spectra, X‐ray powder techniques and their morphology by SEM measurements. The cyclic voltammetric results show that the cathodic peak (E_pc) potential of (3) shifts towards more positive values compared with that of (2) as a result of the BPh₂⁺‐bridged complex formation. The Suzuki–Miyaura reaction was used to investigate their activity as catalyst either prepared in‐situ or from well‐defined complexes. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and characterization of the [Ru(η5-C5Me4CF3)(CO)2]2 and Ru6(μ3-H)(η2-μ4-CO)2(μ-CO)(CO)12(η5-C5Me4CF3) complexes

The reaction of Ru₃(CO)₁₂ with tetramethyltrifluoromethylcyclopentadiene at various ratios of the reagents was studied. Refluxing of Ru₃(CO)₁₂ with a sixfold excess of tetramethyltrifluoromethylcyclopentadiene in octane in an inert atmosphere gave a complex, which is, according to X-ray diffraction data, a dimer,trans-[Ru(η⁵-C₅Me₄CF₃)(CO)₂]₂. The reaction under the same conditions but starting from Ru₃(CO)₁₂ and C₅Me₄CF₃H in 2∶1 molar ratio gave a hexaruthenium cluster [Ru₆(μ₃-H)(η₂-μ₄-CO)₂(μ-CO)(Co)₁₂(η⁵-C₅Me₄CF₂)], which was characterized by IR as well as¹H,¹³C, and¹⁹F NMR spectroscopy. According to X-ray diffraction data, an Ru₄ tetrahedron, in which two edges are bound by additional “briding” Ru atoms, constitutes the frame of this compound. This complex has one (η⁵-C₅Me₄CF₃) ligand, as well as one (μ₃-H) and two (η²-μ₄-CO) groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 507–512, March, 1998.