Chemistry of dioxiranes. 12. Dioxiranes

Murray, Robert W.

doi:10.1021/cr00095a013

Cited by 675 publications

(289 citation statements)

References 20 publications

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“…52-56, 62, 68, 69, 89, 90, and 101-107). The primary frontier orbital interaction for both spiro and planar approaches is between the highest occupied molecular orbital of the alkene ( of CAC) and the lowest unoccupied molecular orbital of the dioxirane (* of OOO), which accounts for the electrophilic nature of the dioxirane (52)(53)(54). Both experimental and theoretical studies show that, in general, spiro transition states are favored over planar transition states (52-56, 62, 68, 69, 89, 90, 101-107).…”

Section: Methodsmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

“…[52][53][54]. Chiral dioxiranes were shown recently to be effective for asymmetric epoxidation of trans-, trisubstituted , and certain cis-alkenes (92)(93)(94)(95).…”

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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“…Estes compostos são facilmente preparados a partir de substân-cias comercialmente disponíveis, sendo os métodos mais comuns os que envolvem a oxidação de cetonas por perácidos, particularmente o ácido monoperoxissulfúrico 64,65 .…”

Section: Técnicas De Dessulfuraçãounclassified

Contaminação ambiental por compostos organoestânicos

Godoi

Favoreto²,

Santiago-Silva³

2003

Quím. Nova

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“…The residue was purified by silica gel chromatography. Elution with 30% ethyl acetate/hexane afforded 16β,20α,26-trihydroxy-6β-methoxy-3α,5-cyclo-5α-cholestan-22-one 26-tosylate (12) …”

Section: Oxidation With Dimethyldioxiranementioning

confidence: 99%

Further study on oxidation of pseudosapogenins

Morzycki

2002

Arkivoc

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6β-Methoxy-3α,5-cyclo-5α-furost-20(22)-ene (4) and its 26-tosyloxy derivative (3) were oxidized with m-chloroperoxybenzoic acid, dimethyldioxirane and osmium tetroxide. The reaction of 4 with MCPBA yielded the allylic alcohol 6, the α,β-unsaturated ketone 7 and the α-hydroxy-lactone 8. Similar reaction of 3 carried out in a buffered medium led to the products 9 and 10 with the C20-C22 bond cleaved. The reaction of the same compound with dimethyldioxirane afforded the allylic alcohol 5. The oxidation of pseudosapogenins with OsO 4 gave dihydroxylation products 11 and 12.

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Chemistry of dioxiranes. 12. Dioxiranes

Cited by 675 publications

References 20 publications

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

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

Contaminação ambiental por compostos organoestânicos

Further study on oxidation of pseudosapogenins

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