Oxidation of Silyl Enol Ethers by Using IBX and IBX⋅N-Oxide Complexes: A Mild and Selective Reaction for the Synthesis of Enones

Nicolaou, K. C.; Gray, David; Montagnon, Tamsyn; Harrison, Scott T.

doi:10.1002/1521-3773(20020315)41:6<996::aid-anie996>3.0.co;2-i

Cited by 240 publications

(103 citation statements)

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“…Thus, activation of the ketone group of 22 gave trimethylsilyl enol ether 25 , which served as a common intermediate for all required substrates (Scheme 2). Oxidation of 25 with IBX•MPO19 led to dienone 26 , with deprotection of the TBS ether giving parent prochiral substrate 15 . Alternatively, the oxidation of cyclohexenone 22 could be achieved in a one-pot procedure through the introduction of a phenylselenide group followed by selenoxide formation and syn elimination as summarized in Scheme 2.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of Platensimycin and Related Natural Products

et al. 2009

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Platensimycin (1) is the flagship member of a new and growing class of antibiotics with promising antibacterial properties against drug resistant bacteria. The total syntheses of platensimycin and its congeners, platensimycins B 1 (7) and B 3 (9), platensic acid (2), methyl platensinoate (3), platensimide A (4), homoplatensimide A (5), and homoplatensimide A methyl ester (6) ( Figure 1) are described. The convergent strategy developed toward these target molecules involved construction of their cage-like core followed by attachment of the various side chains through amide bond formation. In addition to a racemic synthesis, two asymmetric routes to the core structure are described: one exploiting a rhodium-catalyzed asymmetric cycloisomerization, and another employing a hypervalent iodine-mediated dearomatizing cyclization of an enantiopure substrate. The final two bonds of the core structure were forged through a samarium diiodide-mediated ketyl radical cyclization and an acid-catalyzed etherification. The rhodium-catalyzed asymmetric reaction involving a terminal acetylene was developed as a general method for the asymmetric cycloisomerization of terminal enynes.

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Section: Resultsmentioning

confidence: 99%

Total Synthesis of Platensimycin and Related Natural Products

et al. 2009

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“…This successfully provided ketone 36 in 70% isolated yield. Ketone 36 was transformed to the corresponding TMS enol ether in 70% yield, however, oxidation of this enol ether with Pd(OAc) 2 50 or IBX51 furnished enone 37 in very low yields (<20%). Ketone 36 was converted to the corresponding selenide with PhSeCl in EtOAc in the presence of 1 drop of concentrated HCl.…”

Section: Resultsmentioning

confidence: 99%

Total Synthesis of (−)-Platensimycin, a Novel Antibacterial Agent

Ghosh

2009

J. Org. Chem.

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An enantioselective synthesis of platensimycin, a novel antibiotic natural product that inhibits bacterial β-ketoacyl-(acyl-carrier-protein) synthase (FabF), is described. Our synthetic strategy for the construction of the oxatetracyclic core involved an intramolecular Diels-Alder reaction. Our preliminary studies provided a complex tetracyclic product, by first undergoing an interesting 1,5-hydride shift followed by a Diels-Alder reaction. Further optimization of the diene's electronic properties, by incorporation of a methoxy group, led to the oxatetracyclic core of platensimycin. The three required chiral centers, including two all-carbon quaternary chiral centers, were built in the intramolecular Diels-Alder step. The synthesis utilized natural (+)-carvone as the key chiral starting material, which determined the stereochemistry of the final product. The synthesis also featured an efficient Petasis olefination, a hydroboration sequence, a Gais's asymmetric Horner-WadsworthEmmons reaction, and a mercury salt catalyzed enol ether isomerization.

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“…225 Moreover, the same transformation can be achieved through a two step procedure, where a silyl enol ether is first obtained and subsequently oxidized with the complex IBX•MPO (Scheme 52). 325 An example of this reaction in an architecturally complex substrate has been reported in the total synthesis of (+)-cortistatin A (Scheme 53). 155,157 Additionally, this methodology was applied in studies toward platensimycin, 283,326,327 platencin, 237 and cylindramide.…”

Section: Scheme 51mentioning

confidence: 99%