Regio- and stereoselective ring-opening reactions of epoxides with indoles and pyrroles in 2,2,2-trifluoroethanol

Aliphatic and aromatic epoxides react regio- and stereoselectively with indoles and pyrroles in 2,2,2-trifluoroethanol without the use of a catalyst or any other additive. While aromatic epoxides are selectively attacked at the benzylic position, aliphatic epoxides react at the less-substituted position. Chiral epoxides react with >99 % ee (ee=enantiomeric excess).     

Mild and Efficient Ring Opening of Epoxides Catalyzed by Potassium Dodecatungstocobaltate(III)

Summary. Efficient ring opening of epoxides under mild conditions is reported. Potassium dodecatungstocobaltate(III) trihydrate was used as an efficient catalyst for the alcoholysis and acetolysis of epoxides. Conversion of epoxides to thiiranes was also performed efficiently in the presence of this catalyst.     

Retro‐Corey‐Chaykovsky Epoxidation: Converting Geminal Disubstituted Epoxides to Ketones

Corey‐Chaykovsky epoxidation has been widely applied in the conversion of aldehydes and ketones to epoxides with sulfonium and sulfoxonium ylides. The reverse transformation is realized for conversion of geminal disubstituted epoxides to ketones in the presence of DABCO in refluxing mesitylene. The method is a weak basic transformation from epoxides to ketones with loss of a methylene group and can be applied as an alternative strategy of the acid‐catalyzed Meinwald rearrangement or oxidation for conversion of epoxides to carbonyl compounds.     

Regio- and stereoselective synthesis of aziridino epoxides from cyclic dienes

Two different routes for the regio- and stereoselective synthesis of aziridino epoxides from cyclic dienes have been explored. The first strategy involves regiospecific aziridination of cyclic diene derivatives and subsequent epoxidation with m-CPBA to yield cis-aziridino epoxides as major products. The second strategy utilizes regiospecific epoxidation of cyclic diene derivatives followed by Sharpless aziridination to provide exclusively trans-aziridino epoxides. Synthesis of both enantiomers of cis-aziridino epoxides from (R)-(-)- and (S)-(+)-carvones are also reported.     

Conversion of epoxides to 1,3-dioxolanes catalyzed by tin(II) chloride

Anhydrous tin(II) chloride is an efficient catalyst for the reaction of epoxides with acetone to prepare 2,2-dimethyl-1,3-dioxolanes (acetonides) in good to excellent yields. Mono-, di-, and trisubstituted epoxides participate equally well in this diastereospecific reaction. The use of single enantiomer epoxides under the reported conditions results in significant erosion of optical activity.     

Multicomponent linchpin couplings. Reaction of dithiane anions with terminal epoxides, epichlorohydrin, and vinyl epoxides: efficient, rapid, and stereocontrolled assembly of advanced fragments for complex molecule synthesis

The development, application, and advantages of a one-flask multicomponent dithiane linchpin coupling protocol, over the more conventional stepwise addition of dithiane anions to electrophiles leading to the rapid, efficient, and stereocontrolled assembly of highly functionalized intermediates for complex molecule synthesis, are described. Competent electrophiles include terminal epoxides, epichlorohydrin, and vinyl epoxides. High chemoselectivity can be achieved with epichlorohydrin and vinyl epoxides. For vinyl epoxides, the steric nature of the dithiane anion is critical; sterically unencumbered dithiane anions afford S(N)2 adducts, whereas encumbered anions lead primarily to SN2' adducts. Mechanistic studies demonstrate that the SN2' process occurs via syn addition to the vinyl epoxide. Integration of the multicomponent tactic with epichlorohydrin and vinyl epoxides permits the higher-order union of four and five components.     

Co(III) porphyrin/DMAP: an efficient catalyst system for the synthesis of cyclic carbonates from CO2 and epoxides

CoTPP(Cl)/DMAP was found to be a highly active catalyst system for the chemical fixation of CO₂ via reaction with epoxides. The corresponding cyclic carbonate products are produced in high yield and selectivity for a variety of terminal mono and disubstituted epoxides. 1,2-Disubstituted internal epoxides were also investigated as substrates and found to react with very high stereospecificity.     

Investigation of the catalytic activity of an electron-deficient vanadium(IV) tetraphenylporphyrin: A new, highly efficient and reusable catalyst for ring-opening of epoxides

In this work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V^IV(TPP)(OTf)₂], in the nucleophilic ring-opening of epoxides is reported. This new V(IV) catalyst was used as an efficient catalyst for alcoholysis with primary (methanol, ethanol and n-propanol), secondary (iso-propanol) and tertiary alcohols (tert-butanol), hydrolysis and acetolysis of epoxides with acetic acid and also for the conversion of epoxides to 1,2-diacetates with acetic anhydride, conversion of epoxides to thiiranes with ammonium thiocyanate and thiourea, and for conversion of epoxides to acetonides with acetone. The catalyst was reused several times without loss of its activity.     

Synthesis of Cyclic Carbonates Catalysed by Chromium and Aluminium Salphen Complexes

Chromium and aluminium salphen complexes have been found to display remarkable catalytic activity in the synthesis of cyclic carbonates from a range of epoxides and carbon dioxide. The Al(salphen) complex is more reactive towards terminal epoxides at ambient temperature and pressure, whereas the Cr(salphen) complex exhibits higher catalytic activity towards more challenging internal epoxides at elevated temperature and pressure.     

Ring opening of epoxides with NaHSO4: isolation of β-hydroxy sulfate esters and an effective synthesis for trans-diols

Sodium hydrogen sulfate (NaHSO₄) was observed to be highly effective as a reagent or catalyst in the ring-opening reactions of epoxides under mild conditions. Reaction of epoxides with NaHSO₄ gave isolable β-hydroxy sulfate esters and vicinal diols. Experimenting with different epoxides, the study investigated the scope of the ring-opening reaction.     

Chemistry of fullerene epoxides: synthesis, structure, and nucleophilic substitution-addition reactivity

Fullerene epoxides, C??O(n), having epoxide groups directly attached to the fullerene cage, constitute an interesting class of fullerene derivatives. In particular, the chemical transformations of fullerene epoxides are expected to play an important role in the development of functionalized fullerenes. This is because such transformations can readily afford a variety of mono- or polyfunctionalized fullerene derivatives while conserving the epoxy ring arrangement on the fullerene surface, as seen in representative regioisomeric fullerene polyepoxides. The first part of this review addresses the synthesis and structural characterization of fullerene epoxides. The formation of fullerene epoxides through different oxidation reactions is then explored. Adequate characterization of the isolated fullerene epoxides was achieved by concerted use of NMR and LC-MS techniques. The second part of this review addresses the substitution of fullerene epoxides in the presence of a Lewis acid catalyst. Most major substitution products have been isolated as pure compounds and their structures established through spectroscopic methods. The correlation between the structure of the substitution product and the oxygenation pattern of the starting materials allows elucidation of the mechanistic features of this transformation. This approach promises to lead to rigorous regioselective production of various fullerene derivatives for a wide range of applications.     

手性（Salen)CO催化的末端环氧化合物水解动力学拆对反应在手性药物合成中的应用

用手性(Salen)Co催化剂催化的外消旋末端环氧化合物的水解动力学拆分反应 所得的手性末端环氧化合物和各种取代的胺和烷氧负离子反应，可得到光学纯的β -胺基醇和β-烷氧基醇类化合物，这两类化合物是重要的生物活性分子．此方法应 用到手性药物T-588(治疗老年痴呆症药)和盐酸左旋沙丁胺醇(治疗哮喘药)的全合 成．     

4,5-环氧环己烷1,2-二甲酸二缩水甘油酯的固化行为

本文用动态力学扭辨分析法,研究4,5-环氧环己烷1,2-二甲酸二缩水甘油酯与间苯二胺的热固化动态力学行为。结果表明:固化过程分两个阶段进行,低于100℃时,交联反应主要在缩水甘油酯链的环氧基上进行;100—130℃时为酯链环氧基反应趋近完全和酯环环氧基反应速率逐步增大的过渡区;130℃以上固化时,酯环环氧基才明显地参与固化交联反应。从Arrhenius关系曲线求得本固化体系凝胶点前表现反应活化能为13.2kcal/mol。     

Asymmetric hydrolytic kinetic resolution with recyclable macrocyclic Co(III)-salen complexes: a practical strategy in the preparation of (R)-mexiletine and (S)-propranolol

A chiral cobalt(III) complex (1e) was synthesized by the interaction of cobalt(II) acetate and ferrocenium hexafluorophosphate with a chiral dinuclear macrocyclic salen ligand that was derived from 1R,2R-(-)-1,2-diaminocyclohexane with trigol bis-aldehyde. A variety of epoxides and glycidyl ethers were suitable substrates for the reaction with water in the presence of chiral macrocyclic salen complex 1e at room temperature to afford chiral epoxides and diols by hydrolytic kinetic resolution (HKR). Excellent yields (47% with respect to the epoxides, 53% with respect to the diols) and high enantioselectivity (ee>99% for the epoxides, up to 96% for the diols) were achieved in 2.5-16 h. The Co(III) macrocyclic salen complex (1e) maintained its performance on a multigram scale and was expediently recycled a number of times. We further extended our study of chiral epoxides that were synthesized by using HKR to the synthesis of chiral drug molecules (R)-mexiletine and (S)-propranolol.     

Studies on quinones. Part 40: Synthesis and cytotoxicity evaluation of anthraquinone epoxides and isomerization products

Aerobic oxidation of 1,4,4a,10a-tetrahydro-1,4-alkano-5,10-anthraquinones and thiophene-analogues in dichloromethane-DBU yielded the corresponding dihydroalkanoquinones which, depending on their structures, react with in situ generated hydroperoxide anion to give quinone epoxides and/or hydroperoxides. The calcium hydroxide-induced rearrangement of quinone epoxides yielded furan-containing angular quinones. The cytotoxic activities of quinone epoxides and their isomerization products were evaluated in vitro against normal human lung fibroblasts (MRC-5) and human cancer gastric epithelial cells (AGS).     

The reactivity of epoxides with lithium 2,2,6,6-tetramethylpiperidide in combination with organolithiums or grignard reagents

The scope and limitations of lithium 2,2,6,6-tetramethylpiperidide (LTMP)-modified reductive alkylation of epoxides is detailed. A variety of organolithiums are added to terminal and 2,2-disubstituted epoxides in the presence of LTMP to generate alkenes in a completely regio- and highly stereoselective manner. Arylated alkenes, dienes, allylsilanes, and enynes are accessed using this procedure. The methodology is applied in the synthesis of the roller leaf moth pheromone, (3E,5Z)-dodecadienyl acetate. The corresponding reaction without LTMP has also been examined, and a study using deuterated epoxides provides insight into the mechanism. In the presence of LTMP, Grignard reagents are also shown to produce E-alkenes directly from epoxides.     

Guanidines as a nitrogen source for direct conversion of epoxides to aziridines

Direct conversion of epoxides to aziridines was achieved with guanidines as a nitrogen source. Stereochemical inversion at the chiral centers of epoxides was observed without loss of optical purity.     

Homologation of Furfural and Deriuatives to Furylacetaldehydes

The homologation of furfural 1a and methyl 3-(5-formyl-2-furyl) propenoate 1b or ethyl 3-(5-formyl-2-furyl) propenoate 1c to the corresponding furylacetaldehydes was carried out in two stages:

i) preparation of the furan epoxides from 1a, 1b, 1c

ii) cleavage and rearrangement of the epoxides on sepiolite. Sepiolite is a convenient catalyst for this last stage involving substrates as labile as the furan epoxides.     

Reaction of oxiranes with lithium: deoxygenation leading to olefins

Mono-, di-, tri- and tetra-substituted epoxides undergo facile deoxygenation yielding olefins when treated with lithium in tetrahydrofuran. Aliphatic epoxides yield olefins with the same stereochemistry as the parent compound.     

A readily synthesized and highly active epoxide carbonylation catalyst based on a chromium porphyrin framework: expanding the range of available beta-lactones

[reaction: see text] Catalytic carbonylation of epoxides to beta-lactones was effected by a highly active and selective bimetallic catalyst comprised of a chromium(III) porphyrin cation and a cobalt tetracarbonyl anion. The complex is readily synthesized from commercially available compounds in high yield. Carbonylation of numerous linear epoxides, as well as bicyclic epoxides derived from 8- and 12-membered hydrocarbons, proceeded with high activity, selectivity, and yield.