Conjugate addition of indoles and thiols with electron-deficient olefins catalyzed by Bi(OTf)3

Conjugate addition of indoles and thiols with a variety of electron-deficient olefins mediated by a catalytic amount of Bi(OTf)₃ at ambient temperature to afford the corresponding Michael adducts in good to excellent yields with high selectivity is reported.     

A novel and stereoselective synthesis of 7α-alkynylestra-1,3,5(10)-triene-3,17β-estradiol

Different stereoselective synthetic routes for the preparation of 7α/β-substituted estradiol derivatives, that is, 7α-alkynylestra-1,3,5(10)-triene-3,17β-estradiol (13) and its 17β-acetate derivative (14), are explored. These steroids are key starting materials for Pd-catalyzed Sonogashira cross-coupling reactions to yield potential estrogen receptor (ER) antagonists, ER-based imaging ligands and other multi-functional agents. Initial preparation of 7α-alkynyl nortestosterone derivatives followed by various approaches to aromatize the A-ring, failed. Instead, stereoselective 7α-cyanation before A-ring aromatization, followed by 7α-cyano reduction to the 7α-aldehyde, dibromomethylenation and dehydrobromination of the aldehyde, gave the desired 7α-alkynyl derivatives 13 and 14 in good yield.     

A facile synthetic method of α-quaternary-β,γ-unsaturated aldehydes via the stereoselective 1,4-elimination and α-regioselective Ferrier reaction

The 1,4-elimination reaction of 2-substituted-(2Z)-4-methoxy-O-alkenyl acetals with n-butyllithium is shown to afford the 2-substituted-(1Z,3E)-O-1,3-dienyl acetals in high stereoselectivities. The Ferrier reaction of the O-1,3-dienyl acetals thus obtained provides the corresponding α-quaternary-β,γ-unsaturated aldehydes in excellent yields with high α-regioselectivities.     

手性β-氨基醇催化α,β-不饱和酮的不对称环氧化反应

将以烯烃为原料通过Sharpless不对称双羟化等多步反应合成的8种手性β-氨基醇, 作为有机小分子催化剂, 用于催化α,β-不饱和酮的不对称环氧化反应．考察了影响对映选择性的催化剂结构、催化剂用量、氧化剂种类、溶剂、反应温度等因素．结果表明, 当催化剂用量为30 mol%、氧化剂为TBHP(叔丁基过氧化氢)、正己烷溶剂、在室温下、以(1S,2R)-(＋)-1,2-二苯基-2-甲氨基乙醇(3)作催化剂时, 所得环氧化物的对映体过量最高为70% ee, 产率最高为84%.     

An efficient synthesis of a biantennary sialooligosaccharide analog using a 1,6-anhydro-β-lactose derivative as a key synthetic block

An efficient and versatile method for the synthesis of a biantennary octasaccharide derivative was established by combined chemical and enzymatic manipulations of 1,6-anhydro-β-lactose as a key starting material. A key 1,6-anhydro-β-lactose derivative having two unprotected hydroxyl groups at C-3′ and C-6′ positions was prepared and employed for the chemical coupling reaction with a known 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl imidate to afford a tetrasaccharide derivative with two GlcNAc branches in 69% yield. Enzymatic galactosylation using UDP-Gal with a bovine milk β1,4-galactosyltransferase and subsequent sialylation with a recombinant α2,3-sialyltransferase in the presence of CMP-Neu5Ac proceeded smoothly and gave a desired model compound, a bivalent sialooctasaccharide (1), in 73% overall yield from the tetrasaccharide intermediate.     

Synthesis of per-2,3-di-O-heptyl-β and γ-cyclodextrins: a new kind of amphiphilic molecules bearing hydrophobic parts

The synthesis of per-2,3-di-O-heptyl-β and γ-cyclodextrins, a new kind of amphiphilic cyclodextrins bearing long and stable hydrophobic chains is described. The products are obtained in a three-step synthesis from natural cyclodextrins in good yield. tert-Butyldimethylsilyl protection of the primary hydroxyl group was found to be stable under the basic conditions required for the nucleophilic substitution of the bromine derivatives. The structure of the new amphiphilic molecules was proved by NMR spectroscopy and mass spectrometry (ESI-MS or MALDI-TOF-MS).     

棒状β—二酮铑配合物液晶的合成与表征

棒状β┐二酮铑配合物液晶的合成与表征万文赵可清关文捷王春燕张良辅＊（中国科学院成都有机化学研究所成都６１００４１）关键词金属有机配合物，液晶，合成，β－二酮１９９７－０３－３１收稿，１９９７－０８－２１修回国家自然科学基金资助项目β－二酮是一种配位能...     

The first preparation of the α-iodo-β,β-difluorovinylzinc reagent (CF2CIZnCl) and a high-yield one-pot synthesis of α-iodo-β,β-difluorostyrenes

The α-iodo-β,β-difluorovinylzinc reagent (CF₂CIZnCl) was synthesized in >87% yield via room-temperature metallation of the commercially available CF₃CH₂I with LDA in the presence of ZnCl₂. This novel zinc reagent upon palladium-catalyzed cross-coupling with aryl iodides produced α-iodo-β,β-trifluorostyrenes (ArCICF₂) in 62-80% isolated yield.     

Crystal structure analysis of β-tricalcium phosphate Ca3(PO4)2 by neutron powder diffraction

The crystal structure of sintered β-tricalcium phosphate, Ca₃(PO₄)₂, was refined using a high-resolution neutron powder diffraction data and the Rietveld method. This material was confirmed to have a rhombohedral structure (space group R3c, Z=21). Unit-cell parameters with higher precision (a=b=10.4352(2) Å, c=37.4029(5) Å, α=β=90°, and γ=120° in the hexagonal setting) and positional parameters for oxygen with equal precision were obtained by the neutron powder diffraction technique, compared with the single-crystal X-ray diffraction data by Dickens et al. (J. Solid State Chem. 10 (1974) 232). The site Ca(4) with atomic coordinates [0.0, 0.0, −0.0851(6)] was confirmed to be very different from the other four Ca sites: The position Ca(4) is three-fold coordinated with oxygen atoms, and has lower occupancy factor of 0.43(4), and a higher isotropic thermal parameter. On the contrary, each of the Ca(1), Ca(2), Ca(3), and Ca(5) is fully occupied by one Ca atom and these positions are coordinated with seven, eight, eight, and six oxygen atoms, respectively. The bond valence sums of Ca(4) and Ca(5) are lower (0.7) and higher (2.7), respectively, than the others (1.8-2.1).     

Nanocrystalline F-doped tin dioxide materials: texture, morphology and photosensitization with a perylene-substituted organotin

The controlled hydrolysis of fluoro(2-methylbutan-2-oxy)di(pentan-2,4-dionato)tin followed by annealing at 400-550 °C gave conductive mesoporous F-doped SnO₂ materials. The materials consist of a porous network of aggregated nanoparticles, the mesoporosity observed corresponding to the interparticle space. Tuning of the annealing temperature enabled us to prepare materials with surface areas ranging from 70 to 150 m² g⁻¹, with an average pore size comprised between 50 and 100 Å and with a mean particle diameter ranging from 50 to 120 Å. Resistivities as low as 1-2 Ω cm were measured for the sample treated at 550 °C which contained 2-3 at.% of fluorine. This powder reacted with 3-(6-trihex-1-ynylstannylhexyl)perylene to furnish a dye-sensitized F-doped SnO₂ mesoporous materials. An intensity-dependent photocurrent was produced under blue light illumination using the cavity microelectrode (CME) technique. With an aqueous NaBr solution, the photopotential reaches 700 mV, a value slightly higher than that found for an undoped sensitized SnO₂ powder (∼600 mV).