Epoxidation Of Electron-deficient Olefins Research Articles

Pyrenediones as versatile photocatalysts for oxygenation reactions with in situ generation of hydrogen peroxide under visible light

Pyrenediones (PYDs) are efficient photocatalysts for three oxygenation reactions: epoxidation of electron deficient olefins, oxidative hydroxylation of organoborons and oxidation of sulfides via in situ generation of H2O2 from O2 under visible light irradiation.

Dramatic Effect of Carboxylic Acid on the Electronic Structure of the Active Species in Fe(PDP)-Catalyzed Asymmetric Epoxidation

The electronic structure of the iron–oxygen intermediates responsible for catalytic transformations in the biomimetic catalyst systems [((S,S)-PDP)FeII(OTf)2]/H2O2/RCOOH has been found to be strongly dependent on the structure of the carboxylic acid RCOOH. For carboxylic acids with primary and secondary α-carbon atoms (acetic acid, butyric acid, caproic acid), the active species exhibit electron paramagnetic resonance (EPR) spectra with large g-factor anisotropy (g1 = 2.7, g2 = 2.4, g3 = 1.7), whereas for those with tertiary α-carbon atoms (2-ethylhexanoic acid, valproic acid, 2-ethylbutyric acid), the active species display EPR spectra with small g-factor anisotropy (g1 = 2.07, g2 = 2.01, g3 = 1.96). The EPR spectra of the latter intermediates are very similar to those of the intermediates previously assigned to oxoiron(V) species. The systems featuring intermediates of the second type ensure higher enantioselection in the epoxidation of electron-deficient olefins.

Chemoselective epoxidation of electron rich and electron deficient olefins catalyzed by meso-tetraarylporphyrin iron(iii) chlorides in imidazolium ionic liquids

The oxygenation of substrates containing both electron rich and electron deficient olefins (1a–b) catalyzed by 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides [TAPFe(III)Cl] with H2O2 gave epoxides at both electron rich and deficient olefin (2a–b, 3a–b), while with iodosyl benzene (PhIO) gave the epoxides only at electron rich olefin (3a–b) in imidazolium ionic liquids (ILs). Further reaction of 2a–b with sodium hydroxide in methanol gave 4a–b by base catalysed rearrangement of enedione epoxides. Similar reaction of 4a–b with H2O2 or PhIO gave the major epoxides of electron deficient olefins and electron rich olefins. The ferric peroxy anions (TAP-FeIII–OO−) are effective intermediates in the epoxidation of electron deficient olefins, whereas the high valent oxoferrylporphyrin π-cation radicals (TAP-FeIVO˙+) are involved in the epoxidation of electron rich olefins. The ILs provide the special microenvironments by the interactions of cations and anions, in which the generation of the active intermediates from TAPFe(III)Cl/[Bmim][PF6] and monooxygen donors could be accelerated significantly.

フッ素のユニークな使い方: フッ素（F<sub>2</sub>）を活性化剤として用いる有機合成化学反応

Fluorinated organic compounds have received increasing attention due to their unique biological nature in medicinal science and peerlessly excellent property in material science. And thus, a lot of methods for synthesizing highly functionalized fluorinated organic compounds and a number of suitably designed fluorinating reagents have been developed in recent years, most of which have been well documented in excellent reviews and books. However, no review on unique utilization of fluorine(F2) for functionalizing or synthesizing fluorine-free organic compounds has been published. This review involves the fluorine-promoted functionalizations such as oxidations of thiophenes to thiophene S,S-dioxides, pyridines and quinolines to the corresponding N-oxides, and amino group to nitro group along with direct hydroxylation and iodination of aromatics, epoxidation of electron-deficient alkenes, and direct functionalization of 2-position of pyridines. Almost instantaneous oxygen transfer reactions under mild conditions and effective generations of hydoxylium and iodonium ion equivalents otherwise impossible characterize the fluorine-promoted functionalizations.

A new chiral diiron catalyst for enantioselective epoxidation

The dinuclear chiral complex Fe(2)O(bisPB)(4)(X)(2)(ClO(4))(4) (X = H(2)O or CH(3)CN) catalyzes with high efficiency (up to 850 TON) and moderate enantioselectivity (63%) the epoxidation of electron deficient alkenes at 0 degrees C by a peracid.

An Immobilized Organocatalyst for Cyanosilylation and Epoxidation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Oligopeptides as catalysts for asymmetric epoxidation

Oligopeptides are versatile catalysts for the enantioselective epoxidation of electron deficient alkenes, (e.g. alpha,beta-unsaturated ketones) with alkaline hydrogen peroxide. This review describes optimisation of the catalyst, substrate range, synthetic applications of the products and rationalisation of the stereoselectivity by an active site model.

Chemoselective Epoxidation of Electron Deficient Enones with Iodosylbenzene.

The epoxidation of electron deficient olefins is demonstrated with PhIO and an assortment of enones.

Chemoselective Epoxidation of Electron Deficient Enones with Iodosylbenzene

The epoxidation of electron deficient olefins is demonstrated with PhIO and an assortment of enones.

PREPARATION, CHARACTERISATION AND APPLICATION OF POLYAMINE-SILICA HYBRIDS IN THE EPOXIDATION OF a ,b -UNSATURATED OLEFINS

Polyamine-silica hybrids were prepared by a one-pot sol-gel method via a neutral amine templating route. At low loadings (ca. 1 mmol organic group per g of silica) the resultant materials displayed properties typical of M41S-type materials, namely, high surface area (typically 600 m2 g-1) and controlled porosity with an average pore diameter of 3.6 nm. However, the materials were amorphous at loading above 1.2 mmol organic group per g of silica. The materials were used as heterogeneous base catalysts in the epoxidation of electron deficient olefins. The yields of the epoxide product ranged between 52% and 76%, depending on the loading of the catalytic group. (Received October 10, 2001; revised February 28, 2001) Bull. Chem. Soc. Ethiop. 2002, 16(1), 103-112

Modified natural phosphates: easily accessible basic catalysts for the epoxidation of electron-deficient alkenes

Natural phosphate is basic enough to promote the epoxidation of electron-deficient alkenes with dilute aqueous hydrogen peroxide. A simple modification with sodium nitrate leads to the probably most active, water compatible and recyclable basic catalyst described for this reaction. It promotes the epoxidation of a large variety of alkenes.

The preparation and use of novel immobilised guanidine catalysts in base-catalysed epoxidation and condensation reactions

Novel guanidine bases supported on silicas and Micelle Templated Silicas (MTS) have been prepared, and investigated in the base catalysed epoxidation of electron deficient alkenes with excellent conversions and selectivities both with respect to the alkene and the primary oxidant. They are also efficient catalysts for the condensation of malonic acid with heptanal.

Asymmetric epoxidation of electron-deficient olefins

In recent years, methods for the asymmetric epoxidation of electron-deficient olefins, particularly α,β-enones, have attracted widespread attention. A critical review is presented of these methods, which include epoxidations with chiral metal hydroperoxides, asymmetric phase-transfer methods, the use of polyamino acid catalysts and the use of chiral dioxiranes.

Epoxidation of Electron Deficient Alkenes Using tert-Butyl Hydroperoxide and 1,5,7-Triazabicyclo[4.4.0]dec-5-ene and its Derivatives

Epoxidation of Electron Deficient Alkenes Using <i>tert</i>-Butyl Hydroperoxide and 1,5,7-Triazabicyclo[4.4.0]dec-5-ene and its Derivatives

KF adsorbed on alumina effectively promotes the epoxidation of electron deficient alkenes by anhydrous t-BuOOH

KF adsorbed on alumina (KF-Al 2O 3) has been studied in detail for the epoxidation of electron deficient alkenes with anhydrous t-BuOOH. Aqueous base sensitive functional groups survive the reagent. Cyclopentenones are oxidized in decent to quantitative yields without showing any observable aldol products. α,β,γ,δ-Dienones are regioselectively oxidized at the α,β-position. Unlike aqueous alkaline H 2O 2, KF-Al 2O 3 is non-stereospecific and offers a mixture of cis and trans oxides from most acyclic enones. Except for the oxidation of α,β-unsaturated lactones and for the difference in reaction rates, the present reagent is, in general, similar to the t-BuOOH-DBU combination.

1,8-diazabicyclo [5.4.0] undec-7-ene: A remarkable base in the epoxidation of α, β-unsaturated-δ-lactones and other enones with anhydrous t-BuOOH

1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) has been studied for the epoxidation of electron deficient alkenes with anhydrous t-BuOOH (TBHP) in dichloroethane. Steric demands are higher than that for alkaline H 2O 2- DBU is recognised as a remarkable base in these oxidations as other bases such as triethyl amine, diisopropylethyl amine, and 1,4-diazabicyclo[2.2.2]octane (DABCO) are absolutely inefficient. DBU is effective in promoting the oxidation of α, β-unsaturated δ-lactones where most of conventional methods either fail or perform poor.

Al 2O 3 supported KF: An efficient mediator in the epoxidation of electron deficient alkenes with t-BuOOH

KF-Al 2O 3 is discovered to promote epoxidation of electron deficient alkenes. Functional groups that are labile to aqueous basic conditions survive. The steric demand for the reaction is higher than that for alkaline H 2O 2.