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Enantioselective de...
Enantioselective deprotometalation of alkyl ferrocenecarboxylates using bimetallic bases
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Dayaker, G. (författare)
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Erb, W. (författare)
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Hedidi, M. (författare)
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Chevallier, F. (författare)
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Blot, M. (författare)
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Gros, P. C. (författare)
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- Hilmersson, Göran, 1966 (författare)
- Gothenburg University,Göteborgs universitet,Institutionen för kemi och molekylärbiologi,Department of Chemistry and Molecular Biology
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Roisnel, T. (författare)
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Dorcet, V. (författare)
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Bentabed-Ababsa, G. (författare)
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Mongin, F. (författare)
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(creator_code:org_t)
- 2021
- 2021
- Engelska.
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 45:48, s. 22579-22590
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https://gup.ub.gu.se...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- The enantioselective deprotometalation of alkyl ferrocenecarboxylates (FcCO(2)R) using mixed lithium-zinc or lithium-cadmium bases is described. By using FcCO(2)Me as the substrate, chiral lithium alkyl-amidozincates prepared from exo-(alpha R)- or endo-(alpha S)-N-(alpha-phenylethyl)bornylamine (H-exo-born-R or H-endo-born-S) were tested; the best results (27% yield and 62% ee in favor of the R-P enantiomer) were obtained by using Bu-2(endo-born-S)ZnLi in tetrahydrofuran (THF) at -30 degrees C before iodolysis. Due to the low compatibility of FcCO(2)Me with alkyl-containing lithium zincates, 1 : 1 mixtures of lithium and zinc amides were tested. Chiral (H-exo-born-R or H-endo-born-S) or/and achiral (lithium 2,2,6,6-tetramethylpiperidide or lithium diisopropylamide) secondary amines gave good results, the best (81% yield and 44% ee in favor of the R-P enantiomer) being obtained by using (endo-born-S)(3)ZnLi in THF at room temperature. Among other secondary amines also prepared and/or tested, commercial (S,S)-bis(alpha-phenylethyl)amine (H-PEA-S) proved promising. After optimization of the reaction conditions, the best enantioselectivity (26% yield and 80% ee in favor of the RP enantiomer) was observed by treating a THF solution of FcCO(2)Me and Zn(PEA-S)(2) with Li-PEA-S at -80 degrees C before iodolysis. That no reaction took place with cadmium instead of zinc suggests the formation of 'ate complexes upon treatment of Cd(PEA-S)(2) by Li-PEA-S while Zn(PEA-S)(2) and Li-PEA-S would rather work in tandem (Li-PEA-S as the base and Zn(PEA-S)(2) as the in situ trap for the formed ferrocenyllithium). While FcCO(2)Me, FcCO(2)tBu and FcCO(2)iPr could be converted into their racemic 2-iodinated derivatives with a yield of 84 to 87% by employing LiTMP (2 equiv.) in the presence of ZnCl2.TMEDA (1 equiv.) as an in situ trap, their enantioselective deprotometalation rather required Li-PEA-S together with Zn(PEA-S)(2) to produce the enantio-enriched derivatives with yields of 45-82% and 71% ee.
Ämnesord
- NATURVETENSKAP -- Kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences (hsv//eng)
Nyckelord
- mixed lithium-cadmium
- diastereoselective deprotonative metalation
- mediated asymmetric-synthesis
- directed ortho-metalation
- planar chiral
- ferrocenes
- chemoselective base
- catalytic synthesis
- ortho-lithiation
- tmp-zincate
- esters
- Chemistry
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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Till lärosätets databas
- Av författaren/redakt...
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Dayaker, G.
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Erb, W.
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Hedidi, M.
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Chevallier, F.
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Blot, M.
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Gros, P. C.
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visa fler...
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Hilmersson, Göra ...
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Roisnel, T.
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Dorcet, V.
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Bentabed-Ababsa, ...
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Mongin, F.
-
visa färre...
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Göteborgs universitet