The jacobsen catalyst derivative, r,rmn3,5dtbutsalhdclo 4 cat 2, was immobilized through axial coordination of the metal center onto a laponite, mcm41 and fsm16 functionalized with 3aminopropyltriethoxysilane. Epoxidation of neralgeranial using a jacobsenkatsuki mn. Simple iron catalyst for terminal alkene epoxidation. In comprehensive asymmetric catalysis, 1st ed jacobsen, e. Highly enantioselective epoxidation with hydrogen peroxide and. Epoxidation of olefins without metal catalysts adv. The jacobsen epoxidation allows the enantioselective formation of epoxides from various cissubstituted olefins by using a chiral mnsalen catalyst and a. Enantioselective epoxidation of unfunctionalized olefins. Mn mediated epoxidation of alkenes the jacobsenkatsuki epoxidation.
The jacobsen epoxidation is a chemical reaction which allows enantioselective synthesis of epoxides from isolated alkenes. Moreover, jacobsen and katsuki epoxidation was very attractive due to a. Jacobsen epoxidation an overview sciencedirect topics. The asymmetric epoxidation of indene using aqueous naocl, catalyzed by jacobsen s chiral manganese salen complex, provides indene oxide in 90% yield and 85. 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. The jacobsenkatsuki epoxidation and its controversial. Radicals or manganaoxetaneswhat are the intermediates in the jacobsenkatsuki epoxidation see scheme on the right. Asymmetric nucleophilic epoxidation organic reactions wiki. Catalytic epoxidation of propene with h 2oo 2 reactants on autio 2w manuel ojeda and enrique iglesia received in cambridge, uk 5th august 2008, accepted 5th november 2008.
These studies led to both confirmatory findings of catalysts for the epoxidation of propylene, such as ag,1,2,4 cu,5 and pd,10 and to the discovery of new leads, such as bi, ru. Jacobsens method of epoxidation of an alkene essay example. It is complementary to the sharpless epoxidation used to form epoxides from the double bond in allylic alcohols. As an application, the formal synthesis of 6s,7s,9r,10r6,9epoxynonadec18ene7,10diol is reported. The catalytic activity of the mnbased materials was screened for the enantioselective epoxidation of three olefins. Epoxidation of olefins without metal catalysts erowid.
In this example, excess tbhp was quenched with triethylphosphite instead of feii sulfate. Takushi nagata, kiyomi imagawa, tohru yamada, teruaki mukaiyama. Jacobsen implies attack on oxospecies occurs from the back face over the diamine bidge katsuki implies that skewed shape of salen complex results in attack from the side small substituent passes axial proton bulky tbu groups block attack from front or sides o mn n n h o h o bulky tbu groups block approach from front. The katsukijacobsen oxidationepoxidation of acyclic. 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. 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.
This diastereoselectivity is a form of substrate control of the reaction finally, epoxidizing agents that possess stereogenic structures can influence the stereochemistry of the epoxide product see for example thesharpless epoxidation and jacobsen epoxidation. It is complementary to the sharpless epoxidation used to form epoxides from the double bond in. An easy method for epoxidation of olefins using bleach sodium hypochlorite and either a stoichiometric or catalytic amount of bromide ion has been developed. The enantioselective epoxidation of unfuctionalized olefins by optically active mniii salen complexes has become a very important and versatile tool for organic. The jacobsen epoxidation gains its stereoselectivity from a c 2 symmetric manganeseiii salenlike ligand, which is used incatalytic amounts. These keywords were added by machine and not by the authors. Jacobsenkatsuki epoxidation organic chemistry portal. The use of the cocatalyst p 3no allowed for a decreased charge of the mn salen catalyst in the jacobsen epoxidation. Catalyzed asymmetric epoxidation reactions by hydrogen. Epoxidation studies of 2styrylchromones using jacobsens. This enantioselectivity is a form of reagent control of the reaction.
Myers sharpless asymmetric epoxidation reaction chem 115 a further example of anomalous stereochemistry in ae of an allylic diol no reaction with dipt. Jacobsens method of epoxidation of an alkene essay sample. The jacobsen epoxidation involves the enantioselective transformation of cissubstututed alkenes to epoxides using a manganesesalen complex as a catalysts. Reaction of the olefin either with hypochlorous acid or with chlorine and water gives the chlorohydrin which subsequently yields the epoxide on alkaline treatment. The axial ligand, 43phenylpropylpyridine noxide p3no, increases the rate of epoxidation without affecting enantioselectivity and also stabilizes the catalyst. 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. Asymmetric synthesis use of a chiral manganese catalyst for the enantioselective epoxidation of alkenes introduction chemists have discovered and developed many elegant and synthetically useful. In this work, we report on a new methodology for the recovery and reutilization of the jacobsen s catalyst in the enantioselective epoxidation of cisethyl cinnamate under homogeneous conditions.
The sharpless epoxidation reaction is considered one of the most powerful advances in asymmetric organic synthesis 1. Mechanistic study of the jacobsen asymmetric epoxidation. Halcon reaction general procedure because of the activating and directive influence of oh groups, allylic alcohols are important starting materials for the halcon reaction. The jacobsen epoxidation, sometimes also referred to as jacobsenkatsuki epoxidation is a chemical reaction which allows enantioselective epoxidation of unfunctionalized alkyl and aryl substituted olefins. It is usually executed in dichloromethane or acetonitrile. The jacobsen epoxidation, sometimes also referred to as jacobsenkatsuki epoxidation is a. Aerobic enantioselective epoxidation of unfunctionalized olefins catalyzed by optically active salenmanganeseiii complexes bulletin of the chemical society of japan 1994, 67 8, 22482256.
P 3no stabilized the catalyst, increased the rate, and transported bulk oxidant hocl into the. The hydrolytic kinetic resolution jacobsens catalyst. Compared to the sharpless epoxidation, the jacobsen epoxidation allows a broader substrate scope for the transformation. The sharpless epoxidation is an organic reaction used to steroselectively convert an allylic alcohol to an epoxy alcohol using a titanium isopropoxide catalyst, tbutyl hydroperoxide tbhp, and a chiral diethyl tartrate det. Enantioselective styrene epoxidation using the jacobsen catalyst immobilized on functionalized sba15 article in studies in surface science and catalysis 158. 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.
Asymmetric synthesis use of a chiral manganese catalyst for the asymmetric epoxidation of styrene introduction chemists have discovered and developed many elegant and synthetically useful transformations of carboncarbon double bonds. Catalytic epoxidation of propene with h oo reactants on. Myers sharpless asymmetric epoxidation reaction chem 115. Generally speaking, the highly enantioselective epoxidation of styrenes still remains a formidable challenge. Thus, this reaction is referred to as the jacobsen. 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 enantioselective epoxidation of unfuctionalized olefins by optically active mn iii salen complexes has become a very important and versatile tool for organic.
While the practical utility of this protocol is indisputable, the mechanistic underpinnings have been the matter of some debate. Asymmetric synthesis use of a chiral manganese catalyst for the enantioselective epoxidation of alkenes juhyun bae third experiment report, university of wisconsin, madison wisconsin 53703 email protected abstract r 4 r 1 r 3 r 2 r 4 r 1 r 3 r 4 r 1 r 2 r 3 o o r 2 or o jacobsens catalyst n n o o mn cl cch 3 3 h 3 c 3 c h 3 c 3 c cch 3 3 jacobsens catalyst is an extremely. 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. Nucleophilic epoxidation methods represent a viable alternative to electrophilic methods, many of which do not epoxidize electronpoor double bonds efficiently. Nucleophilic epoxidation is the formation of epoxides from electrondeficient double bonds through the action of nucleophilic oxidants. Jacobsen reported in 1990 that mn iii complexes of chiral salen ligands 41 were the most efficient catalysts available for the enantioselective epoxidation of alkyl and arylsubstituted olefins. Manganese salen catalysed asymmetric epoxidation of unfunctionalised olefins o o n n mn oac tbu bu ph o o 92% ee 86% ee jacobsen, j. Examples of the sharpless asymmetric epoxidation reaction in industry. Enantioselective epoxidation of alkenes by jacobsen. It is a classic example of the use of an asymmetric catalyst to provide an enantiomerically enriched mixture of epoxy alcohols. The hydrolytic kinetic resolution jacobsens catalyst a cursory introduction enantiomerically pure epoxides are extremely valuable chemical compounds due to controllable but high reactivity of epoxides coupled with the vast array of reactions they can undergo. The procedure typically uses titaniumiv tetraisopropoxide tioipr4 as a catalyst, a peroxide, and dialkyl tartrates to induce asymmetry in the. Implication of an electronic effect on the competition between spiro and planar transition states matthew hickey, david goeddel, zackary crane, and yian shi department of chemistry, colorado state university, fort collins, co 80523.
Show full abstract the jacobsen katsuki epoxidation, based on literature observations, are introduced as a means to analyse the behaviour of 2 and its modulation by the formation of macrocycle 1. Epoxidation via vicinal halohydrins br 2 h 2 o oh naohnaoh corresponds to overall syn addition of oxygen to the double bond br h 3 c h ch 3 o h h h 3 c ch 3 h h ch 3 h 3 c h. The mechanism begins with the displacement of the isopropoxide ligands on the titanium by det, tbhp, and finally by. In addition to the epoxidation of olefins with peracids, the following alternative processes are known. Pdf file of the digital annex containing additional nmr, gc and hplc spectra. Epoxidation studies of 2styrylchromones using jacobsens catalyst and hydrogen peroxide and iodosylbenzene as oxidants clementina m. Enantioselective styrene epoxidation using the jacobsen. This process is experimental and the keywords may be updated as the learning algorithm improves. The present study represents the features of the jacobsen s catalysts and katsuki s catalysts, which have been used in the epoxidation reaction.
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