Journal
CHEMISTRY-A EUROPEAN JOURNAL
Volume 20, Issue 4, Pages 1038-1048Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201303569
Keywords
carbometalation; chelation; copper; cyclopropene; diastereodivergence
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Funding
- German-Israel Project Cooperation (DIP)
- Israel Academy of Sciences and Humanities [140/12]
- Volontariat International Program of the French Embassy
- Israeli Ministry of Foreign Affairs
- WBI (Wallonie Bruxelles International)
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The copper-catalyzed carbomagnesiation reaction of cyclopropenyl esters 1 leads to various substituted cyclopropanes species 3 in good yields with very high diastereoselectivities. The reaction proceeds through a syn-chelated carbomagnesiation reaction and could be extended to various cyclopropenylmethyl ester derivatives 5. The potential of this approach was illustrated by the preparation of two consecutive all-carbon quaternary stereocenters. However, the carbometalation reaction needs to be performed at temperature ranging from -35 to -20 degrees C to avoid subsequent fragmentation reaction into stereodefined ,-nonconjugated unsaturated esters 4. Alternatively, the carbocupration reaction with organocopper species could also be performed to leads to configurationally stable cyclopropyl copper species2[Cu]. Additionally, when the Lewis acid character of the copper center is decreased (i.e., RCuCNLi), the reaction proceed with an anti-selectivity. The diastereodivergent behavior of these organometallic species is of synthetic interest, since both diastereomers syn-3 and anti-3 can be obtained, at will, from the same precursor cyclopropenyl esters 1.
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