- C-H oxygenation at tertiary carbon centers using iodine oxidant
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An oxidation system in which iodic acid (HIO3) is used as an oxidant in the presence of N-hydroxyphthalimide (NHPI) permitted the selective hydroxylation of tertiary C-H bonds and the lactonization of carboxylic acids containing a tertiary carbon center. These reactions are operationally simple and proceed under metal-free conditions using commercially available reagents, thus offering an ideal tool for the efficient oxidation of C-H bonds at tertiary carbon centers.
- Kiyokawa, Kensuke,Ito, Ryo,Takemoto, Kenta,Minakata, Satoshi
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supporting information
p. 7609 - 7612
(2018/07/15)
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- Synthesis of Lactones via C-H Functionalization of Nonactivated C(sp3)-H Bonds
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An electron-deficient amide is utilized as a directing group to functionalize nonactivated C(sp3)-H bonds through radical 1,5-hydrogen abstraction. The γ-bromoamides formed are subsequently converted to γ-lactones under mild conditions. The method described is not limited to tertiary and secondary positions but also allows functionalization of primary nonactivated sp3-hybridized positions in a one-pot sequence. In addition, the broad functional group tolerance renders this method suitable for the late-stage introduction of γ-lactones into complex carbon frameworks.
- Richers, Johannes,Heilmann, Michael,Drees, Markus,Tiefenbacher, Konrad
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p. 6472 - 6475
(2016/12/23)
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- Electroreductive hydrocoupling of activated olefins with ketones or aldehydes in the presence of trimethylchlorosilane
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Electroreductive crossed hydrocoupling of α,β-unsaturated esters with aldehydes or ketones in the presence of trimethylchlorosilane afforded γ-lactones in good yields. Similarly, α,β-unsaturated nitriles gave γ-hydroxynitriles in high yields.
- Shono, Tatsuya,Ohmizu, Hiroshi,Kawakami, Souta,Sugiyama, Hiroshi
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p. 5029 - 5032
(2007/10/02)
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- Three-Carbon Annelations. Regiocontrolled Reactivity of Trimethylsilyl- and Ethoxyethyl-Protected Cyanohydrins. Versatile Homoenolate and Acyl Anion Equivalents
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The trimethylsilyl- (2) and ethoxyethyl- (4) protected cyanohydrins of α,β-unsaturated aldehydes are utilized as three-carbon annelation reagents.Metalated reagent 2 displays exclusive α reactivity with aldehydes and ketones at -78 deg C.Metalated reagent 4 displays exclusive α reactivity at -78 deg C and exclusive γ reactivity at 0 deg C.Reagent 4 thus allows for complete regiocontrol in its addition to aldehydes and ketones which permits selective addition of either a homoenolate or an acyl anion equivalent.Metalation of the α product 11 at -78 deg C with subsequent warming to 0 deg C produces exclusively the γ product, confirming the reversible nature of the addition to the carbonyl.The derived α '-trimethylsiloxy enones 17 (R3=Me3Si), α '-hydroxy enones 17 (R3=H), α '-acetoxyenones 17 (R3=Ac), and γ-lactones 10 are useful cyclopentenone precursors.Treatment of 17 with p-TsOH in toluene at reflux produces cyclopentenones.The reaction proceeds via the postulated intermediacy of a pentadienyl cation 15 which undergoes in situ electrocyclic ring closure.
- Jacobson, Richard M.,Lahm, George P.,Clader, John W.
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p. 395 - 405
(2007/10/02)
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