Peracid oxidation of trimethylsilyl enol ethers: A facile α-hydroxylation procedure

Rubottom, G. M.; Vázquez, Miguel Á.; PELEGRINA, D. R.

doi:10.1016/s0040-4039(01)92153-7

Cited by 320 publications

(150 citation statements)

References 11 publications

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“…Solvent evaporation, alcoholysis with i-PrOH (80°C), gives a 4:1 mixture of stereotriade 57 and its α,β,γ-anti,anti stereomer. This mixture is converted into their kinetic silyl enol ethers and oxidized with mCPBA (Rubottom oxidation [157]), giving 58, which undergoes Mukaiyama aldol coupling with aldehyde 59 [158][159][160] producing alkene 60 (73 %). Ozonolysis of 60 provides an aldehyde that is allylated under Brown's conditions [161].…”

Section: Methodsmentioning

confidence: 99%

Use of sultines in the asymmetric synthesis of polypropionate antibiotics

Vogel

Turks

Bouchez

et al. 2008

Pure and Applied Chemistry

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At low temperature and in the presence of an acid catalyst, SO 2 adds to 1,3-dienes equilibrating with the corresponding 3,6-dihydro-1,2-oxathiin-2-oxides (sultines). These compounds are unstable above -60°C and equilibrate with the more stable 2,5-dihydrothiophene 1,1-dioxides (sulfolenes). The hetero-Diels-Alder additions of SO 2 are suprafacial and follow the Alder endo rule. The sultines derived from 1-oxy-substituted and 1,3-dioxydisubstituted 1,3-dienes cannot be observed at -100°C but are believed to be formed faster than the corresponding sulfolenes. In the presence of acid catalysts, the 6-oxy-substituted sultines equilibrate with zwitterionic species that react with electron-rich alkenes such as enoxysilanes and allylsilanes, generating β,γ-unsaturated silyl sulfinates that can be desilylated and desulfinylated to generate polypropionate fragments containing up to three contiguous stereogenic centers and an (E)-alkene unit. Alternatively, the silyl sulfinates can be reacted with electrophiles to generate polyfunctional sulfones (one-pot, four-component synthesis of sulfones), or oxidized into sulfonyl chlorides and reacted with amines, then realizing a one-pot, four-component synthesis of polyfunctional sulfonamides. Using enantiomerically enriched dienes such as 1-[(R)-or 1-(S)-phenylethyloxy]-2-methyl-(E,E)-penta-1,3-dien-3-yl isobutyrate, derived from inexpensive (R)-or (S)-1-phenylethanol, enantiomerically enriched stereotriads are obtained in one-pot operations. The latter are ready for further chain elongation. This has permitted the development of expeditious total asymmetric syntheses of important natural products of biological interest such as the baconipyrones, rifamycin S, and apoptolidin A.

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Section: Methodsmentioning

confidence: 99%

Use of sultines in the asymmetric synthesis of polypropionate antibiotics

Vogel

Turks

Bouchez

et al. 2008

Pure and Applied Chemistry

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“…Rubottom oxidation [52] of compound 12 and subsequent reduction of the resulting hydroxy ketone 15 afforded the 3α-alcohol 16a and the 3β-alcohol 16b in a ratio of 1:1.7 (Scheme 4). Although crystalline 12 is stable, rapid decomposition occurs under acidic or neutral aqueous conditions, explaining the moderate yield of hydroxy ketone 15.…”

Section: Synthesis Of Cholesterol Derivativesmentioning

confidence: 99%

Regio‐ and Stereospecific Synthesis of Cholesterol Derivatives and Their Hormonal Activity in Caenorhabditis elegans

Schmidt¹,

Doert²,

Goutal³

et al. 2006

Eur J Org Chem

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Cholesterol is essential for the survival of the nematode Caenorhabditis elegans. Recent studies have demonstrated that cholesterol derivatives regulate two processes in the life cycle of worms: controlling molting and inducing a specialized non‐feeding larval stage. However, the chemical structure of the cholesterol‐derived signalling molecules for these or any other functions has not yet been identified. Herein, we describe the regio‐ and stereospecific synthesis of a number of cholesterol derivatives. The lithium–ammonia reduction of 4‐cholesten‐3‐one was utilized to develop a general method for the introduction of diverse functional groups at C‐4α of 5α‐cholestan‐3β‐ol. Stereoselective functionalization at C‐7 was achieved starting from 7‐ketocholesterol derivatives. 6‐Keto‐5α‐cholestan‐3β‐ol was utilized for specific functionalizations at C‐6 and C‐7. The structure–activity relationships of the different cholesterol derivatives have been investigated by feeding worms of different genetic background with these compounds. Our study is the first step in assigning the relationships of hormonal activity in C. elegans on the substitution at different positions of cholesterol. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…Attempted next, the α-hydroxylation of 2b by the oxidation of its corresponding silyl enol ether with a peracid proved less effective (Rubottom hydroxylation). [15] Thus, generation of silyl enol ether 11 by sequential treatment of 2b with TMSOTf in the presence of collidine, in CH 2 Cl 2 at 0°C, followed by the addition of m-CPBA and NaHCO 3 in dry CH 2 Cl 2 at 0°C for 20 min gave desired α-acetoxy ketone 12 in only 29 % isolated yield, together with 39 % of 13 and 25 % of recovered starting material, as portrayed in Scheme 3. Replacement of the oxidant by MTO-H 2 O 2 [16] failed to give the desired acyloin and the starting material was recovered intact.…”

Section: Elaboration Of Tridentate Ligandsmentioning

confidence: 98%