Mangneseiiicatalyzed asymmetric epoxidation of zolefins. Macmillan division of chemistry and chemical engineering, california institute of technology, pasadena, ca 91125, usa received 29 june 2006. Jacobsenkatsuki epoxidation request pdf researchgate. The first report on the epoxidation of olefins with iodosylbenzene as terminal oxidant and mniiisalen complexes as catalyst was published by kochi et al. The jacobsen epoxidation, sometimes referred to as jacobsen katsuki epoxidation is a chemical reaction which allows enantioselective epoxidation of unfunctionalized alkyl and aryl substituted alkenes. Mn mediated epoxidation of alkenes the jacobsen katsuki epoxidation. Various types of reactions were completed to first create and then use jacobsens catalyst in the asymmetric epoxidation of an unknown alkene with bleach in the laboratory.
Only a few years after this key publication an asymmetric version of this epoxidation was reported by the groups of jacobsen 18 and katsuki 19 using chiral mniiisalen. In comprehensive asymmetric catalysis, 1st ed jacobsen, e. Understanding the mechanism of the epoxidation and the origin of asymmetric induction can lead to the development of new efficient catalysts and therefore is actively pursued 519. The enantioselectivity of the jacobsen epoxidation is generally highest with conjugated cyclic olefins as substrates. The enantioselectivity is explained by either a topon approach jacobsen or by a sideon approach katsuki of the olefin. Selectivity enhancement for the jacobsenkatsuki epoxidation in fluorinated solvents. This ph minimizes the amount of side reactions that could occur such as hydrolysis of the epoxide. Rate enhancement and enantioselectivity of the jacobsen. Mechanism in general, three different mechanisms possible for metal oxo epoxidation. Jacobsen epoxidation of hydroxy sulfonyl diene 4a and cyclization with csa. The application of organocatalytic asymmetric epoxidation mohammed i. Asymmetric nucleophilic epoxidation organic reactions wiki. Highly diastereoselective katsuki jacobsen oxidation. Feb 04, 2000 radical intermediates in the jacobsen katsuki epoxidation radical intermediates in the jacobsen katsuki epoxidation cavallo, luigi.
P wipf chem 2320 1 2 15 2006 9 jacobsen katsuki epoxidations jacobsen jacs 1990 112 2801 jacs 1991 1 7063 katsuki thl 1990 31 7345 based on kochi s. Examples of the sharpless asymmetric epoxidation reaction in industry. Myers sharpless asymmetric epoxidation reaction chem 115. The jacobsenkatsuki epoxidation and its controversial. Although the most commonly used asymmetric epoxidation methods the sharpless katsuki, and jacobsen epoxidations rely on the catalytic reactivity of electrophilic oxidants, nucleophilic oxygen sources substituted with a suitable leaving group can also act as epoxidation reagents. Jacobsen katsuki epoxidation prilezhaev reaction shi expoxidation r 1 r 2 aq. The classic example, the weitzscheffer reaction employs hydrogen peroxide under basic conditions z. Jacobsen hydrolytic kinetic reasolution jacobsen hkr. How to predict the stereochemistry in the product and assign the rs configurati. Katsuki jacobsen oxidation epoxidation of acyclic alphasilyloxy sulfinyl dienes, followed by acidpromoted cyclization, leads to 2,5transsulfonyl dihydrofurans with good selectivities. The jacobsenkatsuki epoxidation and its controversial mechanism. Jacobsenkatsuki epoxidation prilezhaev reaction shi expoxidation r 1 r 2 aq.
Jacobsen and coworkers now at harvard university published the first of several important papers on the enantioselective epoxidation of unfunctionalized olefins catalyzed by chiral manganese complexes. Epoxidation of unfunctionalized olefins by mnsalen catalyst. Na me reactions a collection of detailed reaction mechanisms, jie jack li, jacobsen katsuki epoxidation. Alahmdi in the field of research of target natural product synthesis, catalytic asymmetric synthesis has. The jacobsen epoxidation allows the enantioselective formation of epoxides from various cissubstituted olefins by using a chiral mnsalen catalyst and a stoichiometric oxidant such as bleach. Pdf selectivity enhancement for the jacobsenkatsuki.
Jacobsen epoxidation and cyclization with csa of hydroxy sulfinyl diene 3a. The jacobsen and katsuki have reported the improvement of olefin epoxidation, using a sophisticated chiral salen ligand for manganese complexes, which resulted in high enantioselectivity. The jacobsen epoxidation involves the enantioselective transformation of cissubstututed alkenes to epoxides using a manganesesalen complex as a catalysts. Naocl mnsalen catalyst ch 2 cl 2 r 1 r 2 o h h r 1 r 2 r 3 r3co 3 h r 2 o h r 3 r 1 r 1 r 2 oxone h 2 o,ch 3 cn ph 10. Jacobsen epoxidation an overview sciencedirect topics. Epoxidation of neralgeranial using a jacobsenkatsuki mn catalyst by chemical and electrochemical methods 5 compound with significant potential in the pharmaceutical and chemical industries given its broad applications ranging from the generation of citric flavors and aromas to the synthesis of organic macromolecules 2831. Mechanistic study of the jacobsen asymmetric epoxidation.
By changing the catalyst it is now possible to convert simple alkenes to the corresponding epoxide with highasymmetric induction. The asymmetric epoxidation of indene using aqueous naocl, catalyzed by jacobsen s chiral manganese salen complex, provides indene oxide in 90% yield and 85. Jacobsenkatsuki epoxidation organic chemistry portal. These keywords were added by machine and not by the authors. Radicals or manganaoxetaneswhat are the intermediates in the jacobsen katsuki epoxidation see scheme on the right. Selectivity enhancement for the jacobsenkatsuki epoxidation in. They extensively studied different facets of this reaction to convert it into one of the most useful and widely applicable methods for the epoxidation of. The mechanism of the jk epoxidation is not fully understood, but most likely a manganesev species is the reactive intermediate, which is formed upon the oxidation of the mniiisalen complex. The oxidant for the epoxidation is tert butyl hydroperoxide. Ph co2et o o o aco oac h3c ch3 oo o ch h 3 hh ch h 3 o c ch ch3 ch3 oh h c ch 3 ph co2et o h3c ch3 ch3 ch3 ch3 ch3 ch3 oh ho ch3 o o o soojin kwon 1, oxone, dmm, ch3cn, h2o, ph 10. The chiral epoxide synthesized was then characterized with gcms and nmr.
In this example, a stoichiometric amount of titanium and dipt was necessary for high conversion. Epoxidation definition is a conversion of a usually unsaturated compound into an epoxide. Epoxidation of neralgeranial using a jacobsenkatsuki mn. General mechanism o n n o o r 3 r 3 r 2 r r 1 2 r 1 mn still contraversial 97ang2060 possibilities m o r r 1 m o m o r r 1 concerted stepwise radical or polar oxametallocycle oxidations proceed with a degree of scrambling of geometry tbu et ph co 2et tms 99. Mniiisalencatalyzed asymmetric epoxidation of zolefins. The jacobsen epoxidation gains its stereoselectivity from a c 2 symmetric. Radical intermediates in the jacobsen katsuki epoxidation. The report by kochi and coworkers in 1986 that a salen manganeseiii complex mnsalen complex was an efficient epoxidation catalyst for simple olefins 66 quickly led to independent reports from the groups of jacobsen 67 and katsuki 68 that chiral mnsalen complexes could catalyze asymmetric epoxidation reactions. Enantioselective organocatalytic epoxidation using. 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 jacobsen katsuki. The jacobsen epoxidation, sometimes also referred to as jacobsen katsuki epoxidation is a chemical reaction which allows enantioselective epoxidation of unfunctionalized alkyl and aryl substituted olefins. Epoxidation of unfunctionalized olefins by mnsalen. Such symmetry is useful in ligand design, furnishing predictable and repetitive structural units which reduce the number of diastereomeric transition states ho oh o ro o or ti o o e ti o. Apr 20, 2004 highly enantioselective kochijacobsenkatsuki epoxidation of unfunctionalized olefins with mn iii salenbased chiral catalyst provides an efficient route to optically active epoxides 14.
Probing competitive enantioselective pathways operating in the jacobsen katsuki epoxidation. Request pdf jacobsenkatsuki epoxidation mniiisalencatalyzed asymmetric epoxidation of zolefins. Epoxidation of neralgeranial using a jacobsen katsuki mn catalyst by chemical and electrochemical methods 5 compound with significant potential in the pharmaceutical and chemical industries given its broad applications ranging from the generation of citric flavors and aromas to the synthesis of organic macromolecules 2831. Highly enantioselective kochijacobsenkatsuki epoxidation of unfunctionalized olefins with mniiisalenbased chiral catalyst provides an efficient route to optically active epoxides 14. Jacobsen s catalyst was used to catalyze the epoxidation of an unknown alkene with a bleach solution that was buffered in order to maintain a ph of 9. Epoxidation reactions have been established as an important method for. Probing competitive enantioselective pathways operating in. Highly diastereoselective katsuki jacobsen oxidation epoxidation of.
Mechanistic study of the jacobsen asymmetric epoxidation of. Epoxidation studies of 2styrylchromones using jacobsens. While the practical utility of this protocol is indisputable, the mechanistic underpinnings have been the matter of some debate. The manganese atom transfers an oxygen atom from chlorine bleach or similar oxidant. The application of organocatalytic asymmetric epoxidation. This process is experimental and the keywords may be updated as the learning algorithm improves. Jan 01, 2001 a breakthrough was the introduction of chiral manganesesalen catalysts by jacobsen and co. Article pdf available in helvetica chimica acta 924. The asymmetric epoxidation of indene using aqueous naocl, catalyzed by jacobsens chiral manganese salen complex, provides indene oxide in 90% yield and 85. Understanding the mechanism of the epoxidation and the origin of asymmetric induction can lead to the development of new efficient catalysts and. Jacobsens method of epoxidation of an alkene essay example. In this example, excess tbhp was quenched with triethylphosphite instead of feii sulfate. Pdf probing competitive enantioselective pathways operating.
Compared to the sharpless epoxidation, the jacobsen epoxidation allows a broader substrate scope for the transformation. P 3no stabilized the catalyst, increased the rate, and transported bulk oxidant hocl into the. Understanding the mechanism of the epoxidation and the origin of asymmetric induction can lead to the development of new efficient. Epoxidation definition of epoxidation by merriamwebster. The sharpless asymmetric epoxidation only works with allylic alcohols, as illustrated by the conversion of 156 to 157 or 158 to 159. Request pdf radical intermediates in the jacobsen katsuki epoxidation insight into the controversial mechanism of the mn salencatalyzed epoxidation of olefins is provided in a theoretical. In independent work, katsuki and jacobsen showed that asymmetric epoxidation occurs using manganesesalen catalysts in the presence. Application in process chemistry thl 1995, 36, 3993. The jacobsen katsuki epoxidation and its controversial mechanism. The jacobsen epoxidation, sometimes also referred to as jacobsen katsuki epoxidation is a chemical reaction which allows enantioselective epoxidation of unfunctionalized alkyl and aryl substituted alkenes.
In this video, i have discussed about the mechanism of jacobsen epoxidation. Jacobsenkatsuki epoxidation in name reactions in heterocyclic chemistry, li. Mechanism and stereochemistry prediction in jacobsen. The jacobsen epoxidation is a chemical reaction which allows enantioselective synthesis of epoxides from isolated alkenes. The axial ligand, 43phenylpropylpyridine noxide p3no, increases the rate of epoxidation without affecting enantioselectivity and also stabilizes the catalyst. The jacobsen epoxidation gains its stereoselectivity from a c2 symmetric. Dec 22, 2003 radicals or manganaoxetaneswhat are the intermediates in the jacobsenkatsuki epoxidation see scheme on the right.
General mechanism o n n o o r 3 r 3 r 2 r r 1 2 r 1 mn still contraversial 97ang2060 possibilities m o r r 1 m o m o r r 1 concerted stepwise radical or polar oxametallocycle oxidations proceed with a degree of scrambling of geometry tbu et. Sharpless asymmetric epoxidation mcmaster university. The protocol developed by jacobsen and katsuki for the salenmn catalyzed. The sharpless epoxidation allows the enantioselective epoxidation of prochiral allylic alcohols. Jacobsen epoxidation of hydroxy sulfonyl diene ent4a. The jacobsen epoxidation, sometimes also referred to as jacobsenkatsuki epoxidation is a.
Mechanism, references and reaction samples of the jacobsenkatsuki asymmetric epoxidation. Jacobsens method of epoxidation of an alkene essay sample. The reaction is named after its inventor, eric jacobsen, currently of harvard university. The jacobsen epoxidation allows the enantioselective formation of epoxides from various cissubstituted olefins by using a chiral. Katsuki epoxidation and its controversial mechanism. The use of the cocatalyst p 3no allowed for a decreased charge of the mn salen catalyst in the jacobsen epoxidation. The asymmetric induction is achieved by adding an enantiomerically enriched tartrate derivative. Simple alkenes are oxidized with highasymmetric induction the socalled jacobsenkatsuki reaction. Jacobsen s catalyst o o r 4 r 2 r 3 r 1 r 1 r 2 r 3 r 4 o r 1 r 2 r 3 r 4 or.
Pitt chem 2320 jacobsen katsuki epoxidations gradebuddy. Enantioselective organocatalytic epoxidation using hypervalent iodine reagents sandra lee and david w. The enantioselective epoxidation of unfuctionalized olefins by optically active mn iii salen complexes has become a very important and versatile tool for organic. It is complementary to the sharpless epoxidation used to form epoxides from the double bond in allylic alcohols. Jacobsen epoxidation and cyclization with csa of hydroxy sulfinyl diene 2a. Highly enantioselective kochi jacobsen katsuki epoxidation of unfunctionalized olefins with mn iii salenbased chiral catalyst provides an efficient route to optically active epoxides 14. Recent investigations have shown that the mechanism of the epoxidation is strongly dependent on the substitutents of the alkene and on the reaction conditions. The jacobsen epoxidation gains its stereoselectivity from a c 2 symmetric manganeseiii salenlike ligand, which is used incatalytic amounts.
833 296 804 1447 718 445 1313 757 576 1290 1376 602 807 539 433 43 347 539 1359 215 374 1271 122 1435 91 1086 546 689 688 1557 383 57 1082 1120 736 247 370 670 1471 523 407 91 538 99 1001 65