An iterative acetylene-epoxide coupling strategy for the total synthesis of longimicin C

Longimicin C, a naturally occurring annonaceous acetogenin possessing a C₂-symmetrical bis-THF moiety and a short hydrocarbon chain between its THF-containing region and a terminal γ-lactone, was synthesized for the first time. The total synthesis was successfully achieved by an iterative acetylene-epoxide coupling strategy. d-Mannitol was used to establish the bis-THF-containing segment, in which the additional stereochemistries were introduced by Sharpless dihydroxylations and intramolecular Williamson etherifications. Regioselective epoxide-openings by the appropriate terminal acetylenes allowed coupling and elaboration of all four fragments including the introduction of three essential hydroxyls into the proper sites of the target skeleton.     

Prescriptions and Ingredients for Controlled CC Bond Formation with Organometallic Reagents. New synthetic methods (5)

Merits and drawbacks of known carbon-carbon linking procedures are outlined. Two novel methods are discussed in some detail: the copper-catalyzed alkylation of Grignard reagents and reactions with allylpotassium compounds. Both methods provide a very efficient access to saturated, unsaturated, as well as functionally substituted hydrocarbons and moreover permit an astonishing degree of regio- and stereoselective control of olefin synthesis.     

Theoretical studies on the smallest fullerene: from monomer to oligomers and solid States

Hybrid B3LYP and density-functional-based tight-binding (DFTB) computations on the solid-state structures and electronic properties of the C(20) fullerene monomer and oligomers are reported. C(20) cages with C(2), C(2h), C(i), D(3d), and D(2h) symmetries have similar energies and geometries. Release of the very high C(20) strain is, in theory, responsible for the ready oligomerization and the formation of different solid phases. Open [2+2] bonding is preferred both in the oligomers and in the infinite one-dimensional solids; the latter may exhibit metallic character. Two types of three-dimensional solids, the open [2+2] simple cubic and the body-centered cubic (bcc) forms, are proposed. The energy of the latter is lower due to the better oligomer bonding. The open [2+2] simple cubic solid should be a conductor, whereas the bcc solids are insulators. The most stable three-dimensional solid-state structure, an anisotropically compressed form of the bcc solid, has a HOMO-LUMO gap of approximately 2 eV and a larger binding energy than that of the proposed C(36) solid.     

Synthesis and modification of terrylenediimides as high-performance fluorescent dyes

Two new synthetic approaches to terrylenediimides, highly photostable fluorescent dyes, are described. For the first time terrylenediimide has been synthesised in a straightforward procedure that makes large quantities available. The second route includes an efficient cross-coupling reaction followed by a cyclodehydrogenation. Monofunctionalisation of the imide structure allows terrylenediimides now to be coupled with a variety of compounds, for example, by Suzuki cross-coupling, which can lead to an array of terrylenediimides with new functional groups such as hydroxy, amino, or carboxy groups needed to link up with other molecules. The functionalisation in the bay region is used to tune the properties of terrylenediimides and extend the range of applications, for example, by introducing water solubility. These tetrasubstituted terrylenediimides offer, depending on the substituents used, exciting features such as good solubility in common organic solvents, water solubility, or NIR absorption.     

C4/C5烃催化裂解制低碳烯烃的研究进展

从催化剂类型、裂解工艺、催化裂解的影响因素和裂解机理4个方面对国内外C4／C5烃催化裂解制低碳烯烃的研究进行了综述。催化裂解制低碳烯烃催化剂主要采用ZSM-5分子筛系列催化剂，在此基础上发展了酸改性或水热改性高硅ZSM系列分子筛及介孔MCM41分子筛。总结了国内外C4／C5烃的裂解工艺，认为影响催化裂解的主要因素是裂解原料、催化剂类型及工艺条件。目前，裂解机理主要是自由基与碳正离子机理相结合的机理。并简述了本课题组目前有关C4烷烃催化裂解的主要研究进展。     

The structure of 1-formyl-3-phenyl-Δ-pyrazoline in the gas phase (DFT calculations), in solution (NMR) and in the solid state (X-ray crystallography)

The molecular structure of 1-formyl-3-phenyl-Δ²-pyrazoline was determined by X-ray crystallography (triclinic, P-1). The geometry thus obtained was compared with that obtained by DFT calculations. The GIAO method was used to calculate absolute shieldings, which agree conveniently with those measured by ¹³C and ¹⁵N NMR. The title compound appears to be an essentially planar molecule.     

Elucidation of the structures of 3-alkylthio-, 3-benzylthio-, 2-arylthio- and 2-heteroarylthio-N1-(1,3-dimethylbutyl)-N4-phenyl-1,4-phenylenediamines by one- and two-dimensional NMR spectroscopy

Nucleophilic addition of alkyl- and benzylthiols to benzoquinone diimine (1) gave the corresponding 3-alkylthio- or 3-benzylthio-1,4-phenylenediamines (2-5). However, addition of aryl- or heteroarylthiols to 1 formed 2-arylthio- or 2-heteroarylthio-1,4-phenylenediamines (6-14). The structures of 2-14, obtained in 55-91% yields, were confirmed in CDCl3 or DMSO-d6 solution using 1D (NOE difference, coupled 13C NMR spectra, APT and DEPT) and 2D NMR techniques [DQCOSY, NOESY, HETCOR and heteronuclear multiple bond coherence (HMBC)] that resulted in unambiguous proton and carbon NMR resonance assignments. The substituent-induced 13C NMR chemical shift differences were calculated in 2-14 relative to carbon atoms in the model compound N1-(1,3-dimethylbutyl)-N4-phenyl-1,4-phenylenediamine (DMBPPD) (15) (a reduced form of benzoquinone diimine).     

紫外吸收温差光谱法及其应用

用温差光谱法观察系列化合物的紫外吸收温差谱，发现温差谱具有很强的特征性，具有π键的富勒烯Ｃ６０的温差谱峰为负值，负峰的强度样品温差增大而负荷增大，负峰的峰位无明显移。