An Efficient Catalyst for Asymmetric Epoxidation of Terminal Olefins

Collman, James P.; Zhong, Wang; Straumanis, Andrei; Quelquejeu, Mélanie; Rose, Éric

doi:10.1021/ja9818699

Cited by 169 publications

(102 citation statements)

References 17 publications

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“…This may be attributed to greater ease of access to the metal ion for this isomer. [9] 3. The manganese derivative 4 is the analogue of KodadekЈs catalyst.…”

Section: Asymmetric Epoxidation Of Styrenementioning

confidence: 99%

“…This is in agreement with a recent report by Collman. [9] It should also be mentioned that, besides their application in synthetic chemistry, porphyrins have also recently received renewed attention because of their peculiarities as chromophores. They have been introduced as selective probes in complex molecules, providing a sensitive means of investigating stereochemistry through exciton-coupling analysis.…”

Section: Introductionmentioning

confidence: 99%

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Chiral Atropisomeric Metalloporphyrins in the Enantioselective Styrene Epoxidation

Reginato

Bari

Salvadori³

et al. 2000

Eur. J. Org. Chem.

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“…This may be attributed to greater ease of access to the metal ion for this isomer. [9] 3. The manganese derivative 4 is the analogue of KodadekЈs catalyst.…”

Section: Asymmetric Epoxidation Of Styrenementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chiral Atropisomeric Metalloporphyrins in the Enantioselective Styrene Epoxidation

Reginato

Bari

Salvadori³

et al. 2000

Eur. J. Org. Chem.

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“…Various chiral catalysts and reagents have been investigated for the epoxidation of styrenes, including chiral porphyrin complexes (16 -34), chiral salen complexes (35)(36)(37)(38)(39)(40)(41)(42), chiral oxaziridines and oxaziridinium salts (43)(44)(45)(46), and enzymes (47)(48)(49)(50)(51). Metal catalysts such as chiral porphyrin and salen complexes have been studied extensively for the epoxidation of these alkenes, and the enantioselectivities have reached the 80% range in a number of cases (21,23,29,31,37,38,40,41), with 96% enantiomeric excess (ee) being obtained in one case (3,5-dinitrostyrene) (23).…”

mentioning

confidence: 99%

Highly enantioselective epoxidation of styrenes: Implication of an electronic effect on the competition between spiro and planar transition states

Hickey

Goeddel

Crane

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Asymmetric epoxidation of various styrenes using carbocyclic oxazolidinone-containing ketone 3 has been investigated. High enantioselectivity (89 -93% enantiomeric excess) has been attained for this challenging class of alkenes. Mechanistic studies show that substituents on the ketone catalyst can have electronic influences on secondary orbital interactions, which affects the competition between spiro and planar transition states and, ultimately, enantioselectivity. The results described herein not only reveal the potential of chiral dioxirane catalyzed asymmetric epoxidation as a viable entry into this important class of olefins but also further enhance the understanding of the mechanistic aspects of chiral ketone-catalyzed asymmetric epoxidation. Epoxides are important intermediates for the synthesis of complex molecules. Asymmetric epoxidation of prochiral alkenes presents a powerful strategy for the synthesis of enantiomerically enriched epoxides. Great progress has been made in the areas of asymmetric epoxidation of allylic alcohols (1-3), chiral metal complex-catalyzed epoxidation of unfunctionalized alkenes (particularly with conjugated cis-and trisubstituted alkenes) (4 -7), and asymmetric epoxidation of electron-deficient alkenes under nucleophilic conditions (8 -10). Styrene oxides are extremely useful and can be prepared by a number of methods such as asymmetric reduction of ␣-halo acetophenones (refs. 11 and 12 and references therein), asymmetric dihydroxylation of styrenes (13,14), and kinetic resolution of racemic epoxides (15). The asymmetric epoxidation of styrenes also has received a considerable amount of interest. Various chiral catalysts and reagents have been investigated for the epoxidation of styrenes, including chiral porphyrin complexes (16 -34), chiral salen complexes (35-42), chiral oxaziridines and oxaziridinium salts (43-46), and enzymes (47-51). Metal catalysts such as chiral porphyrin and salen complexes have been studied extensively for the epoxidation of these alkenes, and the enantioselectivities have reached the 80% range in a number of cases (21,23,29,31,37,38,40,41), with 96% enantiomeric excess (ee) being obtained in one case (3,5-dinitrostyrene) (23).Among other oxidants, dioxiranes either isolated or generated in situ are powerful epoxidation agents (Scheme 1; refs. 52-54). Chiral dioxiranes were shown recently to be effective for asymmetric epoxidation of trans-, trisubstituted (55-91), and certain cis-alkenes (92-95). Asymmetric epoxidation of styrenes with chiral dioxiranes has been studied also (61,66,68,81,88,90,(93)(94)(95); however, the enantioselectivity has not exceeded 85% (93-95). Generally speaking, the highly enantioselective epoxidation of styrenes still remains a formidable challenge.During our studies, we found that varying the catalyst structure could have a dramatic effect on enantioselectivity for the dioxirane-mediated epoxidation of styrene. Fructosederived ketone 1 (Scheme 2), a very effective catalyst for transand trisubstituted alkenes, gave only 24...

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“…59 Using a biarylstrapped chiral directing group, epoxides of >90% ee were formed, generally in yields in excess of 73% using as little as 0.1 mol% catalyst. Styrene itself was epoxidised in up to 83% 25 ee, and the method was versatile enough to be extended to a series of structurally-similar substrates with similar selectivities.…”

Section: ) Oxidation Reactions Of Alkenesmentioning

confidence: 99%