Fluorinated epoxides: 6. Chemoselectivity in the preparation of 2-[(heptafluoroisopropyl)methyl]oxirane from iodoacetate and iodohydrin precursors

Fluorinated iodoacetate (CF₃)₂CFCH₂CHICH₂OAc (1) (prepared by radical addition of perfluoroisopropyl iodide to allyl acetate) and fluorinated iodohydrin (CF₃)₂CFCH₂CHICH₂OH (2) (prepared from 1) were converted to the corresponding perfluoroalkylated oxirane (CF₃)₂CFCH₂CH(O)CH₂ (3) in the yield of 62%. The chemoselectivity of the oxirane formation appeared to be strongly dependent on the starting compound 1 or 2 and solvent used. Byproducts (CF₃)₂CFCHCHCH₂OH (4) and (CF₃)₂CFCHCHCH₂OAc (5) can form a major part of the products in the formation of epoxide 3.     

三正丁基膦参与的二苯联硒与吖啶及环氧化合物的开环反应

Aziridines and epoxides were reacted with diphenyl diselenide in the presence of a stoichiometric amount of （n-Bu）3P, respectively, giving β-amino- or β-hydroxy selenides in moderate to excellent yields under mild conditions. In the reactions the （n-Bu）3P might act as a reductant though it was a nucleophilic catalyst in other similar ring-opening reactions.     

Stability of (C60)2 and epoxide dimers, (C60)2ON, and their anions

The PM3, AM1, and MINDO3 semiemperical methods are used to calculate the the energy difference between C60ON and C60ON- and the bond dissociation energy necessary to cleave neutral and negatively charged (C60)2 dimers and epoxide dimers, (C60)2ON, to their respective monomers C60, and C60ON/2. The results show that the anions of the dimers are significantly more stable than neutral dimers. This result may explain the higher thermal stability of the observed ferromagnetic phase in photolyzed C60. which has been attributed to epoxide dimers and oligomers. It also provides an explanation for the origin of unpaired electron spin necessary for ferromagnetism.     

用手性二环氧化物合成手性双膦配体

不对称催化反应,特别是手性双膦配体与过渡金属形成络合物的均相催化氢化反应取得了极为满意的结果。已报道的许多结构简单、活性高、不对称诱导作用好的手性双膦配体,几乎都是通过亲核取代或 Diels-Alder 反应合成的。然而在碱性条件下,亲核取代反     

Preparation of double metal cyanide compleces from water-insoluble zinc compounds and their catalytic performance for copolymerization of epoxide and CO2

A novel method was developed for preparing double metal cyanide complexes based on Zn₃[Co(CN)₆]₂ with water-insoluble zinc compounds such as ZnO, Zn(OH)₂ and basic ZnCO₃ as precursors. The complexes obtained exhibited nearly double catalytic efficiency for the copolymerization of propylene oxide and CO₂ as compared with the complexes originating from the solution precipitation method.     

An efficient synthesis of N-protected threo (2R,3S)-3-amino-1,2-epoxy phenylbutane

A precise and versatile method was developed for the synthesis of threo amino epoxide derivatives, which are useful intermediates for protease inhibitors. It involves the diastereoselective reduction of the carbonyl group of γ-N,N-dibenzyl amino α-hydroxy β-keto sulfide prepared from an amino acid, and its subsequent stereospecific conversion to an amino epoxide via acetoxy halogenation in high yield.     

Regio- and stereoselective ring opening of vinyl epoxides with MgBr2

The regio- and stereoselective ring opening of vinyl epoxides has been achieved by the use of Lewis acid, MgBr₂, affording bromohydrins in excellent yield, which are readily transformed to azidoalcohol, a key intermediate of several classes of pyrrolizidine and indolizidine alkaloids. The scope and limitations of the reaction are discussed.     

Asymmetric Epoxidation of Non-Functionalized Alkenes Using Transition Metal Complexes

Asymmetric catalytic epoxidation of alkenes such as styrenes, chromenes and indene using transition metal complexes both inhomogeneous and heterogeneous phase has been discussed in this review. The various strategies to make the catalysts recyclable by introducing in-built phase transfer ability, converting these to dimeric form, exchanging into clays and supporting on polymeric or inorganic supports are discussed at length.     

Preparation and Optical Properties of Silica-Poly(ethylene oxide) Hybrid Materials

Structural evolution and optical properties of the silica-poly(ethylene oxide) hybrid films prepared from -glycidoxypropyltrimethoxysilane (GPTS) and 1-methylimidazol (MI) are studied. Polymerization of the epoxy groups is achieved by using 1-methylimidazol as a thermal curing agent. In liquid state ¹H &¹³ C NMR spectroscopy, it is found that silica condensation mainly occurs without epoxy ring opening. The epoxide polymerization is confirmed by using FT-IR, solid state CP-MAS ¹³C-NMR, and differential scanning calorimetry (DSC). The hybrid material is densified due to the epoxide polymerization as well as silica condensation with thermal curing. As a result, the thermal curing increases refractive index and extinction coefficient and shifts UV optical absorption edge to longer wavelength.     

Heteropolyacid-catalyzed Reaction of Epoxides with Ketones： Efficient Synthesis of 1,3-Dioxolane Derivatives

An efficient method for the preparation of 1,3-dioxolanes via the coupling of epoxides with ketones catalyzed by heteropolyacids at ambient temperature has been described.