Construction of bicyclic systems containing an oxygen bridge by isomerization of cyclic epoxy alcohols

A novel method for constructing a 7-oxabicyclo[2.2.1]heptane skeleton was developed. The substrates, namely cis-3,4-epoxy-1-cyclohexanol derivatives, were prepared from the corresponding 3-cyclohexen-1-ol derivatives via a stereoselective epoxidation reaction using a vanadium catalyst. Upon heating with lithium iodide in propionitrile, the cis-epoxy alcohol was transformed into the 7-oxabicyclo[2.2.1]heptane derivative in high yield. The reaction proceeds through formation of a lithium alkoxide bearing an iodohydrin moiety, followed by an intramolecular S_N2 reaction.     

Ce-Beta分子筛的制备及其催化性能

采用简单、易重现的两步后合成法成功制备了Ce-Beta分子筛。制备过程中, H-Beta分子筛首先经过脱铝处理得到Si-Beta分子筛,然后再以异丙醇铈为前驱体,通过干法浸渍的途径向Si-Beta分子筛引入Ce (IV)。利用XRD, FT-IR, UV-Vis和1H MAS NMR等对其结构进行了表征,结果表明, Ce(IV)物种以四配位的形式成功引入Beta分子筛的骨架, Ce原子进入分子筛骨架的机理通过DRIFT光谱得以证实。通过环氧化合物水合制备1,2-二醇反应对所制的Ce-Beta催化剂进行了催化性能评价。     

Ultrasonic activated efficient method for the cleavage of epoxides with aromatic amines

An improved protocol for the cleavage of epoxides with aromatic amines in the presence of FeCl₃ promoted by ultrasonic irradiation. This new methodology provides excellent yields in short reaction times (15–25 min) at room temperature.     

Asymmetric Total Synthesis of Stagonolide G

A simple asymmetric total synthesis of stagonolide G ( 1 ) is described. Asymmetric dihydroxylation, regioselective epoxide ring opening, and vinyl Grignard reactions are involved in generating the stereogenic centers C(4) and C(8), followed by Grubbs‐II‐catalyzed ring‐closing metathesis (RCM).     

Functionalization of multi-walled carbon nanotubes by epoxide ring-opening polymerization

In this study, covalent functionalization of carbon nanotubes (CNTs) was accomplished by surface-initiated epoxide ring-opening polymerization. FT-IR spectra showed that polyether and epoxide group covalently attached to the sidewalls of CNTs. TGA results indicated that the polyether was successfully grown from the CNT surface, with the final products having a polymer weight percentage of ca. 14-74 wt%. The O/C ratio of CNTs increased significantly from 5.1% to 29.8% after surface functionalization of CNTs. SEM and TEM images of functionalized CNTs exhibited that the tubes were enwrapped by polymer chains with thickness of several nanometers, forming core-shell structures with CNTs at the center.     

Convenient synthesis of 5-aryl(alkyl)sulfanyl-1,10-phenanthrolines from 5,6-epoxy-5,6-dihydro-1,10-phenanthroline, and their activity towards fungal β-d-glycosidases

A broad series of novel 5-aryl(alkyl)sulfanyl-1,10-phenanthrolines has been prepared by a new simple procedure: a treatment of the commercially available 5,6-epoxy-5,6-dihydro-1,10-phenanthroline with various thiols in the presence of a base. Other functional groups attached to the thiol allow a use of the products as building blocks in synthesis of versatile ligands and in functionalization of surfaces. The synthesized phenanthrolines showed a moderate ability as activators or inhibitors of fungal β-d-glucosidases and β-d-galactosidases.     

Oxidation reactions using polymer-supported 2-benzenesulfonyl-3-(4-nitrophenyl)oxaziridine

A thermally stable polymer-supported oxidant has been developed. Polymer-supported 2-benzenesulfonyl-3-(4-nitrophenyl)oxaziridine was applied to microwave-assisted reactions that occurred at high temperatures and was shown to oxidize alkenes, silyl enol ethers, and pyridines to the corresponding epoxides and pyridine N-oxides in excellent to good yields and with much shorter reaction times. It also enabled tetrahydrobenzimidazoles to be oxidatively rearranged to spiro fused 5-imidazolones in a more efficient manner. Recycling of the polymer-supported oxidant is also possible with minimal loss of activity after several reoxidations.     

Synthesis of stereodefined fused δ-hydroxy-γ-lactones from dealkylative cyclization of epoxy-diesters

A dealkylative lactonization of stereodefined aryl-substituted epoxides allows the preparation of densely functionalized fused δ-hydroxy-γ-lactones having three consecutive stereochemically defined stereocenters.     

One-pot synthesis of thia-Michael products from thio acids, epoxides, and electron-deficient alkenes promoted by a silica gel/Et3N combined catalyst

An efficient method for the one-pot production of thia-Michael adducts using thio acids, epoxides, and electron-deficient alkenes is described. Epoxides quickly underwent nucleophilic ring-opening with thio acids on the silica gel surface at room temperature under solvent-free conditions to yield β-hydroxy thioester intermediates. After addition of an electron-deficient alkene and a catalytic amount of Et₃N to the reaction mixture, the β-acyloxy mercaptans were generated in situ and subsequently underwent thia-Michael addition reactions to produce the corresponding adducts in good to excellent yields.     

双波长微板法测定细胞悬浮液中的环氧化物

用双波长微板法研究了缓冲溶液与细胞悬浮液中吸光度与环氧化物浓度的关系,通过分析比较发现,在两种体系中的回归曲线相互平行。据此,可用缓冲体系中所测结果绘制标准曲线,计算细胞悬浮液中环氧化物的含量。在建立了双波长微板法测定混浊体系中环氧化物的基础上,环氧化物水解酶活力可以方便快速的检测。