Oxidation of silyl enol ethers using 2-sulfonyloxaziridines. Synthesis of .alpha.-siloxy epoxides and .alpha.-hydroxy carbonyl compounds

Davis, Franklin A.; Sheppard, Aurelia C.

doi:10.1021/jo00381a051

Cited by 72 publications

(23 citation statements)

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“…The direct activation of the enol form of keto derivatives has recently been introduced as a new synthetic methodology to achieve ␣-amination (9) or, as already mentioned, ␣-halogenation (2)(3)(4)(5). So far, the only straightforward enantioselective ␣-hydroxylation is the reaction of enolate salts with enantiopure N-sulfonyloxaziridines, acting as electrophilic oxygen sources, as developed by Davis (10,11). However, despite considerable efforts in the area of synthetic methods toward ␣-hydroxycarbonyl derivatives (refs.…”

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confidence: 99%

Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Toullec

Bonaccorsi

Mezzetti

et al. 2004

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

128

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The enantioselective formation of a quaternary stereogenic center coinciding with a hydroxylation process is a very rare reaction from a homogeneous catalysis point of view. Indeed, to our knowledge, no asymmetric transition-metal-catalyzed direct hydroxylation has been reported before. We describe here our initial study concerning the enantioselective ␣-hydroxylation of various ␤-ketoesters catalyzed by Lewis-acidic complexes. Specifically, it was found that the Ti complex [TiCl2((R,R)-1-Np-TADDOLato)(MeCN)2] affords the hydroxylated products in high yield and enantioselectivities up to 94% enantiomeric excess when using 2-(phenylsulphonyl)-3-(4-nitrophenyl)oxaziridine as the oxidizing agent. Chiral enantiopure compounds of the latter type have been used previously in stoichiometric asymmetric hydroxylation reactions. We also show that, in a complementary approach with H2O2 as the oxidant, the Ru(II) complex [RuCl(OE 2)((S,S)-PNNP)]PF6 catalyzes the same type of transformation in a case of substrates showing a very substantial extent of enolization under reaction conditions; being, however, unreactive toward only weakly enolized ␤-ketoesters.R eactions involving both the formation of new carbonheteroatom bonds and the concomitant generation of a new stereogenic center are prototypical transformations in asymmetric catalysis. Thus, for example, hydroboration, hydrosilylation, epoxidation, and aziridination of olefins, as well as allylic substitutions with heteroatom nucleophiles, have been extensively studied (1). However, catalytic halogenations, in particular fluorinations, and direct hydroxylations have received much less attention in the asymmetric catalysis community.Recently, we developed an enantioselective catalytic process in which ␤-ketoesters are fluorinated at the 2-position with an electrophilic fluorine donor such as Selectfluor [also called F-TEDA (TEDA, triethylenediamine), 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis{tetrafluoroborate}] in the presence of a Lewis-acidic chiral titanium catalyst (1, Scheme 1, Fig. 1 (2-5). Our work inspired further developments involving chiral Pd catalysts (6) and chiral phase transfer catalysts for the same type of fluorination (7).The ␣-hydroxycarbonyl functional unit is ubiquitous in natural products and bioactive compounds, such as, e.g., carbohydrates, antibiotics, and antitumor agents; therefore, it is also present in synthetic intermediates and in chiral auxiliaries in view of the stereodirecting ability of the hydroxy group (8). The ␣-functionalization of carbonyl compounds most often relies on the reaction of enolate anions, or enol derivatives with electrophiles. The direct activation of the enol form of keto derivatives has recently been introduced as a new synthetic methodology to achieve ␣-amination (9) or, as already mentioned, ␣-halogenation (2-5). So far, the only straightforward enantioselective ␣-hydroxylation is the reaction of enolate salts with enantiopure N-sulfonyloxaziridines, acting as electrophilic oxygen sources, as dev...

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confidence: 99%

Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Toullec

Bonaccorsi

Mezzetti

et al. 2004

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

128

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“…Next, oxidation of the intermediate 7 proceeded with remarkable selectivity with dimethyldioxirane (DMDO)24a–c to furnish only the expected C6 α‐hydroxylated product 8 25. Of the several different oxidizing agent screened ( m CPBA, Davis oxaziridine,24d chromyl chloride,24e osmium tetroxide,24f methyltrifluoromethyldioxirane,24g and DMDO), DMDO was the most efficacious. The hydroxylated product 8 underwent lactonization on silica gel purification or acid treatment to provide 11 in 49 % overall yield 26.…”

Section: Methodsmentioning

confidence: 99%

Access to Guaianolides: Highly Efficient Stereocontrolled Total Synthesis of (±)‐Geigerin

Carret

Deprés

2007

Angewandte Chemie

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“…They noticeably found applications in organomagnesium compound hydroxylation, [16] alkene epoxidation, [17] sulfide to sulfoxide oxidation, [18] amine to hydroxylamine oxidation, [19] but remain mostly known for enolate [20] or enol surrogates, such as silyl enol ethers, [21] to α-hydroxy ketone oxidations. Furthermore, recent reports [22] highlighted the possibility to obtain dearomatized 2,2-disubstituted cyclohexanone products from phenols under either cationic (CPTC) or anionic (APTC) phasetransfer catalysis in the presence of an adequate electrophile (Scheme 2).…”

Section: Introductionmentioning

confidence: 99%

Phase‐Transfer‐Catalyzed Oxaziridine‐Mediated Hydroxylative Phenol and Naphthol Dearomatization

Grandclaudon

Toullec

2015

Eur J Org Chem

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Oxidation of silyl enol ethers using 2-sulfonyloxaziridines. Synthesis of .alpha.-siloxy epoxides and .alpha.-hydroxy carbonyl compounds

Cited by 72 publications

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Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Access to Guaianolides: Highly Efficient Stereocontrolled Total Synthesis of (±)‐Geigerin

Phase‐Transfer‐Catalyzed Oxaziridine‐Mediated Hydroxylative Phenol and Naphthol Dearomatization

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Oxidation of silyl enol ethers using 2-sulfonyloxaziridines. Synthesis of .alpha.-siloxy epoxides and .alpha.-hydroxy carbonyl compounds

Cited by 72 publications

References 0 publications

Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Expanding the scope of asymmetric electrophilic atom-transfer reactions: Titanium- and ruthenium-catalyzed hydroxylation of β-ketoesters

Access to Guaianolides: Highly Efficient Stereocontrolled Total Synthesis of (±)‐Geigerin

Phase‐Transfer‐Catalyzed Oxazirid­ine‐Mediated Hydroxylative Phenol and Naphthol Dearomatization

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Phase‐Transfer‐Catalyzed Oxaziridine‐Mediated Hydroxylative Phenol and Naphthol Dearomatization