- Sml2-promoted reformatsky-type reaction and acylation of alkyl 1-chlorocyclopropanecarboxylates
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(Chemical Equation Presented) In the presence of HMPA in THF, highly stereoselective Sml2-promoted substitutions of alkyl 1-chlorocyclopropanecarboxylates 1 using various ketones, aldehydes (Reformatsky-type reaction), and acyl chlorides (acyla
- Nagano, Takao,Motoyoshiya, Jiro,Kakehi, Akikazu,Nishii, Yoshinori
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supporting information; experimental part
p. 5453 - 5456
(2009/06/28)
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- Reactions of aliphatic ketones R2CO (R = Me, Et, iPr, and tBu) with the MCl4/Li(Hg) system (M = U or Ti): Mechanistic analogies between the McMurry, Wittig, and Clemmensen reactions
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Analysis of the products of the reactions of ketones R2CO (R = Me, Et, iPr, tBu) with the MCl4/Li(Hg) system (M = U, Ti) at 20°C revealed significant differences. For R = Me, the reaction proceeded exclusively (M = U) or preferentially (M = Ti) via a metallopinacol intermediate resulting from dimerization of ketyl radicals. Pinacol was liberated by hydrolysis, and tetramethylethylene was obtained after further reduction at 65°C. For R = iPr, formation of iPr2C=CiPr2 as the only coupling product, the nonproduction of this alkene by reduction of the uranium pinacolate [U]-OCR2CR2O-[U] (R = iPr) at 20°C, and the instability of the corresponding titanium pinacolate towards rupture of the pinacolic C-C bond indicated that reductive coupling of iPr2CO did not proceed by dimerization of ketyl radicals. Formation of 2,4-dimethyl-2-pentene was in favor of a carbenoid intermediate resulting from deoxygenative reduction of the ketyl. These results revealed that for sterically hindered ketones, McMurry reactions can be viewed as Wittig-like olefination reactions. For R = tBu, no coupling product was obtained and the alkane tBu2CH2 was the major product. The involvement of the carbenoid species [M]=CtBu2 was confirmed by its trapping with H2O, leading to tBu2CH2, and with the aldehydes RCHO, giving the cross-coupling products tBu2C=C(R)H (R = Me, tBu). Therefore, in the case of severely congested ketones, McMurry reactions present strong similarities to the Clemmensen reduction of ketones, owing to the involvement in both reactions of carbenoid species which exhibit similar reactivity. Wiley-VCH Verlag GmbH, 2001.
- Villiers, Claude,Ephritikhine, Michel
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p. 3043 - 3051
(2007/10/03)
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- Direct Preparation of Lanthanoid Ester Homoenolates from 3-Halo Esters and Lanthanoid Metals: Their Homo-Reformatsky-Type Reaction with Carbonyl Compounds
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The direct reaction of ethyl 3-bromopropionate (2a) or 3-iodopropionate (2b) with lanthanoid metals (La, Ce, Nd, Sm) in tetrahydrofuran produces lanthanoid ester homoenolates (3), which react with ketones to give γ-lactones in good yields under mild conditions.The isolation of 3-phenylseleno (8a), 3-phenyltelluro (8b), and 3-tri-n-butylstannyl esters (10) from the reaction with diphenyl diselenide (7a), ditelluride (7b), and tri-n-butyltin iodide (9), respectively, suggests the formation of the lanthanoid ester homoenolate.
- Fukuzawa, Shin-ichi,Sumimoto, Norifumi,Fujinami, Tatsuo,Sakai, Shizuyoshi
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p. 1628 - 1631
(2007/10/02)
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- TiCl4/Mg/BrCH2CH2Br Reagent System: A 1,2-Diorganometallic Equivalent
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1,2-Diorganometallic species generated utilizing the TiCl4/Mg/BrCH2CH2/Br reagent system reacts with ketones to give the corresponding 1,4-diols and/or 1,2-diols in moderate yields.
- Rao, S. Achyutha,Periasamy, M.
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p. 1583 - 1586
(2007/10/02)
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- Magnesium- and Titanium-induced Reductive Coupling of Carbonyl Compounds: Efficient Syntheses of Pinacols and Alkenes
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Finely dispersed magnesium on graphite was found to be a totally selective single-electron transfer reagent of general utility for the reduction of various kinds of carbonyl and dicarbonyl compounds to pinacols, a reaction quite compatible with a number of functional groups.Similarly, titanium on graphite proved to be a universally applicable reducing agent for the efficient conversion of pinacols, carbonyl and dicarbonyl compounds into alkenes and cycloalkenes respectively and for the cyclization of oxo alkanoates to enol ethers, facilitating and unifying the highly useful McMurry reaction.The practicability of the presently known carbonyl coupling methods is discussed in the light of these results.
- Fuerstner, Alois,Csuk, Rene,Rohrer, Christian,Weidmann, Hans
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p. 1729 - 1734
(2007/10/02)
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- A Simple and Efficient New Synthesis of Vicinal Diols by Reductive Coupling of Carbonyl Compounds
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A universally applicable, new 'pinacolic reduction' for aldehydes and ketones is described.
- Csuk, Rene,Fuerstner, Alois,Weidmann, Hans
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p. 1802 - 1803
(2007/10/02)
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- THE APPLICATION OF FREE RADICALS TO THE CATALYTIC SYNTHESIS OF CARBON MONOXIDE DERIVATIVES
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The chemical reactions of carbon monoxide with (C2H5)2Mg and C2H5MgBr in the presence of the carbonyls Mo(CO)6, W(CO)6, Co2(CO)8 and Fe2(CO)9 in tetrahydrofuran have been examined.Catalytic reaction produced a series of compounds.The tetrahydrofuranyl-2-ethyl ketone was the main reaction product, indicating the radical character of the reaction.
- Sobota, Piotr,Kaczurba, Eleonora
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p. 295 - 300
(2007/10/02)
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