Iron-catalyzed preparation of trifluoromethyl substituted vinyl- and alkynylcyclopropanes

A convenient iron-catalyzed procedure to prepare trifluoromethylated vinyl- and alkynylcyclopropanes in a chemo- and diastereoselective manner is presented. The active diazo compound (trifluoromethyl diazomethane) is generated in situ and used in the concomitant cyclopropanation reaction.     

全氟丙烯的齐聚反应

本文综述了氟离子和π-二芳烃铬(0)催化齐聚全氟丙烯的反应。当以氟离子为催化剂时,得到二种二聚体(D-1和D-2)和三种三聚体(T-1,T-2和T-3)的混合物;当以π-二芳烃铬(0)为催化剂时,除生成二聚体(D-1和D-2)和三聚体(T-2和T-3)外,还得到二种脱氟三聚体T-4和T-4′。本文分别讨论了上述两类反应的机理。     

Hypohalogenation of vinyl- and allylacetylenes and some chemical transformations of the products

Hypohalogenation of 2-methylhex-5-en-3-yn-2-ol, 2-methylhept-6-en-3-yn-2-ol, and their methyl ethers at 303–328 K with hydrochloric or hydrobromic acid in the presence of hydrogen peroxide involves only the double bond to produce the corresponding halohydrins in fairly high yields. Kinetic parameters of these reactions were determined, and the allylacetylenic alcohol and its methyl ether were found to be more reactive than their vinylacetylenic analogs. Acetylenic halohydrins and oxiranes derived therefrom were shown to be quite reactive compounds which may be used as building blocks in organic synthesis.     

Zirconium Catalyzed Ethylene Oligomerization

A review of the scientific and patent literature on oligomerization of ethylene to linear olefins in the presence of homogenous or heterogeneous zirconium complexes and various aluminum organic compounds has been fulfilled for last twenty-five years. Over these years, a wide range of studies had been conducted for selective oligomerization of ethylene into a narrow fraction of linear α-olefins such as C₄-C₈ and C₆-C₁₀ fractions. During the discussion of these catalytic systems, exceptional attention is also paid to feature works such as the activity of the catalysts and the acquisition of clear liquid product without any trace of polymer, all of which play important roles in the selection of the best technology.     

Oligomerization of phenylacetylene on fe-catalysts

Using a low activity system as a catalyst gives additional opportunities for study of polymerization mechanism. We made an attempt using phenylacetylene as a monomer to synthesize, separate, and identify oligomers of this alkyne on melting iron catalyst—“naked” metal. Four components with the lowest molecular weight were identified as: (compound 1) isomers of 1,2-diphenylcyclobutadiene, (compound 2) 1,3-diphenylcyclobutadiene, (compound 3) 1,4-diphenylbuten-1-yne-3, and (compound 4) triphenyl substituted Dewar benzene. It was shown, that in the presence of iron catalysts the phenylacetylene oligomerization proceeds as a linear polymerization through a 2 + 2 cycloaddition.     

Reaction of vinyl- and propenyl-ethers with tert-butoxyl radicals - an ESR study

Photolytically generated tert-butoxyl radicals react with vinyl- and propenyl ethers by hydrogen abstraction and addition to the double bond; the abstraction/addition ratio and the regioselectivity of addition are interpreted in terms of predominant steric interactions.     

Stabilisation des vinyl- et ethynyl-phosphines secondaires par complexation du phosphore

A stable divinylphosphine P-W(CO)₅ complex is prepared in 2 steps from the corresponding divinyl-diethylaminophosphine complex by cleavage of the P-N bond by HCl followed by reduction of the P-Cl bond thus formed by LiAlH₄; a similar scheme is used for the synthesis of stable tungsten complexes of vinyl- and phenylethynyl-diethylaminophosphines.     

Oxidative dihydroxylation of alicyclic unsaturated hydrocarbons with vinyl- and norbornene fragments in pseudohomogenic system

Oxidation of alicyclic unsaturated hydrocarbons (4-vinylcyclohexene, 5-vinylnorbornene, 5-cyclohexenylnorbornene, and 5-vinylbicyclooctene) with 30% hydrogen peroxide solutions and percarbamide is studied. Reaction was carried out at 40–70°C in the presence of heterogenized peroxocomplex compounds of molybdenum and tungsten formed “in situ” in the reaction of metal oxohalides with H₃PO₄, nano-dimensional particles of carbon material, and hydrogen peroxide. Main oxidation products of alicyclic diene hydro-carbons are the corresponding unsaturated epoxides and diols. Depending on the reaction condition their ratio varies in a wide range.     

Oligomerization and structural variation of alkali metal silyloxides

Lithium and potassium silyloxide complexes [Li(OSiPh₃)]_n (1), [K(thf)_0.2 (OSiPh₃)]_n (3) and [K(OSiMe₂^tBu)]_n (6) were prepared by deprotonation of HOSiPh₃ or HOSiMe₂^tBu with [Li(ⁿBu)] in hexane or KH in THF, respectively. Crystalline DME adducts [Li(μ-OSiPh₃)(η²-DME)]₂ (2) and [K₄(μ₃-OSiPh₃)₃(μ₃-OSiPh₂(η¹-Ph))(η²-DME)]₂ (μ-DME) (4) were prepared by dissolving 1 or 3, respectively, in dimethoxyethane followed by precipitation with alkane. The potassium-sequestered complexes [K(18-crown-6) (OSiPh₃)]₂ (5) and [K(18-crown-6)(OSiMe₂^tBu)]_n (7) were prepared from 3 or 5, respectively, and one equiv. of 18-crown-6 ether. The complexes were characterized by single-crystal X-ray diffraction: [Li(μ-OSiPh₃)(η²-DME)]₂ (2): a dimer featuring tetrahedral lithium centres linked by bridging —OSiPh₃ ligands. [Crystal data ( − 156°C): space group P , a = 14.238(6), b = 15.182(7), c = 11.796(5) Å, α = 110.57(2), β = 112.02(2), γ = 63.02(1) Å, V = 2055.33 ų, Z = 2.] [K₄(μ₃-OSiPh₃)₃{μ₃-OSiPh₂(η¹-Ph)}(η²-DME)]₂(μ-DME) (4): (1) two cubanes each having every potassium vertex chemically distinct; (2) one chelating DME ligand, one DME ligand bridging between two cubanes; and (3) a K-ipso-phenyl carbon contact. [Crystal data ( − 133°C): a = 14.246(4), b = 30.939(9), c = 17.981(5) Å, β = 112.33(1)° with Z = 2 in space group P2₁/c.] [K(18-crown-6)OSiPh₃]₂ (5): A dimer with slipped face-to-face stacking of the quasi-planar K(18-crown-6)⁺ part of the two Ph₃SiOK(18-crown-6) molecules; these are linked by a dative bond from one ether oxygen of a given crown to potassium contained in the other crown. [Crystal data ( − 155°C): a = 9.324(2), b = 17.640(5), c = 18.148(15) Å, β = 91.60(1)° with Z = 4 in space group P2₁/c.]     

血红素蛋白二聚、寡聚与多聚

血红素蛋白在生物体系中执行多种重要的生物功能,如氧贮存和运输、电子传递、生物催化和生物传感等。尽管大多数血红素蛋白是以单体形式存在,一些血红素蛋白在体外和/或体内,还会形成同源聚合物。本文综述了血红素蛋白的二聚、寡聚与多聚研究进展,包括肌红蛋白、细胞色素c、胞红蛋白,细胞色素b₅、细胞色素b₅₆₂、亚硝酸盐还原酶、血红素传感蛋白和血红素转运蛋白等,着重介绍其结构与功能以及多聚体分子设计的方法与应用。这些研究进展,一方面增强了我们对生物体系中血红素蛋白结构与功能关系的认识,另一方面也赋予了我们通过多聚方法设计功能蛋白来调控和利用血红素蛋白的能力。