This paper describes an enantioselective epoxidation of terminal olefins using chiral ketone 3 as catalyst and oxone as oxidant. For example, a cytochrome p450 bm3 mutant 93 has been developed using directed evolution, which exhibits high activity towards epoxidation of several nonnatural substrates. Pdf merge combine pdf files free tool to merge pdf online. Merge pdf files combine pdfs in the order you want with the easiest pdf merger available. The fructosederived ketone 2 described herein is a member of a class of ketones designed to contain the following general features. Epoxidation definition, a reaction that yields an epoxide. The shi epoxidation is a chemical reaction described as an asymmetric epoxidation of olefins with oxone potassium peroxymonosulfate and a fructosederived catalyst 1. Lignin modification by epoxidation has been studied and the resulting products have been characterized 12. Launch the software, enter in your search term into the. These are not indefinitely stable, but can be generated in situ by.
Organocatalytic asymmetric epoxidation and aziridination of ole. The sharpless asymmetric epoxidation represents another procedure for controlling facial selectivity in epoxidations of allylic alcohols and thus for overcoming intrinsic substrate facial selectivity through catalyst control. Diastereoselective epoxidation may be achieved through the use of alkene starting materials with diastereotopic faces. Seekfast also lets you easily search for your terms in various file types including pdf. The sulfate as a good leaving group facilitates the ring closure to the dioxiranes. Catalytic asymmetric epoxidation of alkenes has been the focus of many research efforts over the past two decades, the best known methods probably being. Studies on the regio and diastereoselective epoxidation of. An efficient catalytic asymmetric epoxidation method. Shi epoxidation wikipedia wikipedia yian shi group.
Myers department of chemistry and chemical biology, harvard university, cambridge, massachusetts 028 received february 18, 2009. These keywords were added by machine and not by the authors. How to search for text inside multiple pdf files at once. Click, drag, and drop to reorder files or press delete to remove any content you dont want. It is complementary to the sharpless epoxidation used to form epoxides from the double bond in allylic alcohols. An efficient catalytic asymmetric epoxidation method journal of. The shi epoxidation is a chemical reaction described as the asymmetric epoxidation of alkenes. This is the case with manganesesalen catalyzed epoxidation of cinnamate esters with. The catalyst is easily prepared from fructose and displays broad generality. Studies on the regio and diastereoselective epoxidation of daphnanes and tiglianes. The jacobsen epoxidation gains its stereoselectivity from a c 2 symmetric manganeseiii salenlike ligand, which is used incatalytic amounts. Files are available under licenses specified on their description page. The asymmetric epoxidation of alkenes using the in situ generated chiral dioxirane formed from the fructosederived ketone precatalyst and oxone potassium peroxymonosulfate is called the shi epoxidation.
When racemic 3isopropylcyclohexene was subjected to dmd oxidation, the trans epoxide, which resulted from attack on the less hindered face of the double bond, was the major product. For example, mcdonald and coworkers recently reported a robust and selective synthesis of 2amino3,5diols that employs the shi epoxidation in a key step scheme 5. The shi epoxidation allows the synthesis of epoxides from various alkenes using a fructosederived organocatalyst with oxone as the primary oxidant. Asymmetric epoxidation of olefins presents an especially attractive approach to chiral epoxides. Scope and limitation article pdf available in letters in organic chemistry 87. A method for the preparation of differentiated trans1,2diol. It is proposed that the shi epoxidation proceeds through a dioxirane intermediate and a spiro transition state and that a socalled. Chem 6352 directed epoxidations all figures and schemes from hoveda, evans, fu chem.
Shi asymmetric epoxidation up to trisubstituted olefins r ch3 o o o o o o h3c h3c ch3 ch3. Please, select more pdf files by clicking again on select pdf files. Directed epoxidations all figures and schemes from hoveda, evans, fu chem. Epoxidation with dioxiranes organic reactions wiki. Examples of the sharpless asymmetric epoxidation reaction in industry. Once windows has finished indexing your pdfs and their contents, youll be able to search for text inside multiple pdf files at once use seekfast to search pdf files. This ring approximates an equilateral triangle, which makes it strained, and hence highly reactive, more so than other ethers.
Asymmetric epoxidation of various styrenes using carbocyclic. This procedure generates epoxides with high enantiomeric excesses from transdisubstituted alkenes and trisubstituted alkenes. Enantioselective epoxidation of terminal olefins by chiral. Using nmrspectroscopy, we investigate why certain peroxides engage in this type of reaction while others require activation by metal catalysts, e. It is an organocatalyst with oxone typically used as the primary oxidant. Myers sharpless asymmetric epoxidation reaction chem 115 a further example of anomalous stereochemistry in ae of an allylic diol no reaction with dipt.
Catalytic asymmetric epoxidation of alkenes has been the focus of many research efforts over the past two decades, the best known methods probably being those developed by sharpless 1 and jacobsenkatsuki. A convenient and environmentally attractive onepot twostep process for the synthesis of. Other groups have used shis methodology in pursuit of a number of unique structural moieties. Once you merge pdfs, you can send them directly to your email or download the file to our computer and view. Files available from the acs website may be downloaded for personal use only. The reaction proceeds under basic conditions and within a. How to merge pdfs and combine pdf files adobe acrobat dc. It is proposed that the shi epoxidation proceeds through a dioxirane intermediate and a spiro transition state and that a socalled planar transition state is a main competing pathway. Epoxidation with in situ prepared manganese based homogeneous catalysts 69 stepwise mechanism route b operates, rotation around the former double bond in 6 can cause isomerization during reaction leading to the obtainment of transepoxides from cisolefins.
The shi epoxidation is a chemical reaction described as the asymmetric epoxidation of alkenes with oxone potassium peroxymonosulfate and a fructosederived catalyst 1. The reaction provides oxindole derivatives possessing chiral epoxides in good yield with good diastereoselectivity and excellent enantioselectivity. Studies on the regio and diastereoselective epoxidation. Organocatalytic asymmetric epoxidation and aziridination of olefins. The addition of the sulfate group by the oxone facilitates the formation of the dioxirane by acting as a good leaving group during ring closure. Epoxidation definition is a conversion of a usually unsaturated compound into an epoxide. Ready enantioselective epoxidation with dioxiranes several groups have developed chiral ketones as catalysts for asymmetric epoxidation. The epoxidation of ethylene involves its reaction of oxygen according to the following stoichiometry. Download and install the software on your computer. This article describes a highly effective catalytic asymmetric epoxidation method for olefins using potassium peroxomonosulfate oxone, dupont as oxidant and a fructosederived ketone 1 as catalyst. Media in category shi epoxidation the following 12 files are in this category, out of 12 total. H 2o 2 ch 3cn may also be used as stoichiometic oxidant. This reaction is thought to proceed via a dioxirane intermediate, generated from the catalyst ketone by oxone potassium peroxymonosulfate. Oxygen transfer in electrophilic epoxidation probed by 17o.
A method for the preparation of differentiated trans1,2diol derivatives with enantio and diastereocontrol sang min lim, nicholas hill, and andrew g. An asymmetric epoxidation using a fructosederived chiral ketone. Sharplesskatsuki asymmetric epoxidation sharpless ae. They are produced on a large scale for many applications. Peroxide compounds are used both in laboratory and industrial processes for the electrophilic epoxidation of olefins. An epoxide is a cyclic ether with a threeatom ring. Zip file containing the mol files of the most important compounds in this article. The jacobsen epoxidation is a chemical reaction which allows enantioselective synthesis of epoxides from isolated alkenes.
To change the order of your pdfs, drag and drop the files as you want. Chiral ketonecatalyzed asymmetric epoxidation of olefins michael frohn, yian shi department of chemistry, colorado state university, fort collins, co 80523, usa. Cornwall, and yian shi department of chemistry, colorado state university, fort collins, colorado 80523, united states contents 1. Epoxidation with in situ prepared manganese based homogeneous. Diastereomeric control in the epoxidation with peracids is quite good, if appropriate directing groups are present, or if the substrate is sterically biased. Epoxidation with in situ prepared manganese based homogeneous catalysts 69 stepwise mechanism route b operates, rotation around the former double bond in 6 can cause isomerization during reaction leading to the obtainment of transepoxides from cis olefins. Click add files and select the files you want to include in your pdf. Rearrange individual pages or entire files in the desired order. This process is experimental and the keywords may be updated as the learning algorithm improves. Representative epoxidation procedure mecnh 2o2, see figure 6 to a solution of trans stilbene 0. The direct reaction of oxygen with alkenes is useful only for this epoxide.
A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Kinetic resolution in asymmetric epoxidation using iminium. Organocatalytic asymmetric epoxidation and aziridination. A method for the preparation of differentiated trans1,2. The catalysis with small molecules, where an inorganic element is not a part of the active principle i. The reaction proceeds under basic conditions and within a mild temperature range 0. High enantioselectivies have been obtained for transdisubstituted and trisubstituted olefins which can bear functional groups such as tributylsilyl ether, acetal, chloride, and ester. Once files have been uploaded to our system, change the order of your pdf documents. The requisite chiral c17c29 subunit was assembled stereoselectively via keck allylation, shi epoxidation, diastereoselective 1,3. Epoxidation definition of epoxidation by merriamwebster.
Isotope effects and the nature of enantioselectivity in the shi epoxidation. Dioxiranes are remarkably versatile oxidizing agents that. In this example, excess tbhp was quenched with triethylphosphite instead of feii sulfate. Epoxidation is a reaction that creates an epoxide, cyclic ether compound containing a three atom ring. Metal mediated epoxidation is remarkably diverse, with many types of ligand systems being represented. Chiral ketonecatalyzed asymmetric epoxidation of olefins. Shi asymmetric epoxidation chiral dioxirane strategy. What links here related changes upload file special pages permanent link page information wikidata item cite this page.
Mn mediated epoxidation of alkenes the jacobsenkatsuki epoxidation. Modified heterogeneous silver catalysts are typically employed. Request pdf asymmetric epoxidation epoxides are strained threemembered heterocycles of extraordinary importance as versatile synthetic intermediates to. These are not indefinitely stable, but can be generated in situ by oxidation of a ketone with potassium peroxymonosulfate oxone. Ketone 1 is an effective catalyst for the epoxidation of a variety of trans and trisubstituted olefins, 3 vinylsilanes, 4 hydroxy alkenes, 5 dienes, 6 enynes, 7 enol ethers, and enol esters. In this example, a stoichiometric amount of titanium and dipt was necessary for high conversion. Asymmetric epoxidation reactions with the advent of the sharpless asymmetric epoxidation reaction, developed in late 70s and early 80s, the epoxidation of both functionalized and unfunctionalized olefins has become an extremely important method for the synthesis of optically active compounds. Epoxide opening reactions recent advances and synthetic. Myers sharpless asymmetric epoxidation reaction chem 115. You can merge pdfs or a mix of pdf documents and other files. However, the molecular weight of lignin ranged 250 kda results in high.
Usa home product directory chemical synthesis asymmetric synthesis chiral catalysts, ligands, and reagents epoxidation chemistry products new chemistry products. Faster epoxidation in 2, 7 fold as smpo process exothermic epoxidation and hydrogenation, heat recovery key of economy. Asymmetric epoxidation of 1,1disubstituted terminal olefins by. Asymmetric epoxidation of cis and trisubstituted olefins by ketone 3da. The synthesis and use of ketone 1 was reported in the original organic syntheses articles. An asymmetric epoxidation using fructosederived chiral ketone. Reaction under shi epoxidation conditions with catalyst 8 and ent8. However 15 years later, in 1980 the sharpless asymmetric epoxidation was discovered as a good example of the stereoselective epoxidation of alkenes, using a protocol to achieve full stereochemical control for such an important and key. The epoxidizing species is believed to be a dioxirane, which is a powerful epoxidation reagent.
1255 1164 64 533 844 1327 1512 265 1076 695 363 1653 301 587 1009 38 690 1444 950 1022 67 663 1102 323 1270 1644 1634 1472 834 1047 1454 94 1443 397 421 310 236 1228 112 199 1084 1239 269