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Olefin epoxidation, asymmetric catalysis

The past thirty years have witnessed great advances in the selective synthesis of epoxides, and numerous regio-, chemo-, enantio-, and diastereoselective methods have been developed. Discovered in 1980, the Katsuki-Sharpless catalytic asymmetric epoxidation of allylic alcohols, in which a catalyst for the first time demonstrated both high selectivity and substrate promiscuity, was the first practical entry into the world of chiral 2,3-epoxy alcohols [10, 11]. Asymmetric catalysis of the epoxidation of unfunctionalized olefins through the use of Jacobsen s chiral [(sale-i i) Mi iln] [12] or Shi s chiral ketones [13] as oxidants is also well established. Catalytic asymmetric epoxidations have been comprehensively reviewed [14, 15]. [Pg.447]

Initial successes with these ligands came independently from the groups of Jacobsen and Katsuki in the asymmetric epoxidation of unfimctionalized olefins. Since these seminal works in 1990, metal salen complexes have become workhorse in asymmetric catalysis, finding applications in a wide variety of reactions. In Figure 1 is illustrated a variety of metal salen complexes. Scheme 1 lists some of the transformations in which they have been used, demonstrating the broad utility of these complexes. [Pg.272]

Only partial solutions have been provided thus far to many of the most important transformations amenable to asymmetric catalysis. For example, no generally effective methods exist yet for enantioselective epoxidation or aziridination of terminal olefins, or for hydroxylation of C-H bonds of any type. Despite the enormous advances in asymmetric hydrogenation catalysis, highly enantioselective reduction of dialkyl ketones remains elusive [9]. And as far as asymmetric C-C bond-forming reactions are concerned, the list of successful systems is certainly shorter than the list of reactions waiting to be developed. [Pg.1378]

Asymmetric catalysis as a synthetic tool is relatively new (if enzymatic reactions are not considered) its development began 10 years ago, mainly because of the advances in coordination chemistry. Asymmetric hydrogenation started by modifying the Wilkinson catalyst (J). The early results (2,3,4) were encouraging enough to initiate a very large amount of research (5,6). Asymmetric C-C bond formation in olefin co-dimerization was observed for the first time by Wilke and his coworkers (7). Asymmetric hydroformylation (8) as well as several new asymmetric alkylation reactions appeared in the last five years (9,10). Asymmetric epoxidations were described in 1977 (11,12). [Pg.51]

Thus, the asymmetric catalysis of cyanoethoxycarbonylation, cyanophosphoryla-tion, epoxidation of electron-deficient olefins, Michael reactions of malonates and (3-keto-esters, Strecker reaction of keto-imines, conjugate addition of cyanide to a, (3-unsaturated pyrrole amides, ring opening of meso aziridines with TMSCN and cyanosilylation of ketones (example shown below) have been successfully carried out using these complexes as asymmetric catalysts. [Pg.528]

The catalytic asymmetric epoxidation of electron-deficient olefins, particularly a,P-unsaturated ketones, has been the subject of numerous investigations, and as a result a number of useful methodologies have been elaborated [44], Among these, the method utilizing chiral phase-transfer catalysis occupies a unique position in terms of its practical advantages. Moreover, it also allows the highly enantioselective epoxidation of trans-a,P-unsaturated ketones, particularly chalcone. [Pg.108]

It should be noted that the related imine-oxaziridine couple E-F finds application in asymmetric sulfoxidation, which is discussed in Section 10.3. Similarly, chiral oxoammonium ions G enable catalytic stereoselective oxidation of alcohols and thus, e.g., kinetic resolution of racemates. Processes of this type are discussed in Section 10.4. Whereas perhydrates, e.g. of fluorinated ketones, have several applications in oxidation catalysis [5], e.g. for the preparation of epoxides from olefins, it seems that no application of chiral perhydrates in asymmetric synthesis has yet been found. Metal-free oxidation catalysis - achiral or chiral - has, nevertheless, become a very potent method in organic synthesis, and the field is developing rapidly [6]. [Pg.277]

The first successful achievements using asymmetric homogeneous transition metal catalysis were obtained in the asymmetric hydrogenation of alkenes24 25, This method has been successfully used in many synthetic applications (Section D.2.5.1.)26-29. In addition, chirally modified versions of the transition metal catalyzed hydrosilylation of olefins and carbonyl compounds (Sections D.2.3.1. and 2.5.1.) and olefin isomerization (Section D.2.6.2.) have been developed. Transition metal catalyzed asymmetric epoxidation constitutes one of the most powerful examples of this type (Section D.4.5.2.). [Pg.286]

In the case of terminal olefins, asymmetric epoxidation typically results in relatively low enantiomeric excess. For (salen)Mn(III) catalysis, it is not clear whether the low degree of asymmetric induction is due to poor enantiofacial selectivity during... [Pg.46]


See other pages where Olefin epoxidation, asymmetric catalysis is mentioned: [Pg.1]    [Pg.362]    [Pg.156]    [Pg.362]    [Pg.196]    [Pg.1232]    [Pg.657]    [Pg.56]    [Pg.146]    [Pg.340]    [Pg.712]    [Pg.712]    [Pg.400]    [Pg.385]    [Pg.186]    [Pg.521]    [Pg.48]    [Pg.13]    [Pg.406]    [Pg.1180]    [Pg.152]    [Pg.122]    [Pg.80]    [Pg.281]    [Pg.204]    [Pg.244]    [Pg.107]    [Pg.8]    [Pg.1]    [Pg.155]   
See also in sourсe #XX -- [ Pg.25 ]




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Asymmetric catalysis

Asymmetric epoxidation

Asymmetric epoxidation catalysis

Asymmetric olefination

Catalysis epoxidation

Catalysis olefins

Epoxidations catalysis

Epoxidations, asymmetric

Epoxides asymmetric epoxidation

Olefin asymmetric

Olefinic epoxides

Olefins asymmetric catalysis

Olefins asymmetric epoxidation

Olefins epoxidation catalysis

Olefins epoxides

Olefins, epoxidation

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