title: Modulable and highly diastereoselective carbometalations of cyclopropenes.
abstract: 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 °C to avoid subsequent fragmentation reaction into stereodefined β,γ-nonconjugated unsaturated esters 4. Alternatively, the carbocupration reaction with organocopper species could also be performed to leads to configurationally stable cyclopropyl copper species 2[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.
authors: Schulich Faculty of Chemistry and the Lise Meitner-Minerva, Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa 32000 (Israel), Fax: (+972) 4 829 3709.
authors: Dorian
authors: D
authors: Didier
authors: Pierre-Olivier
authors: PO
authors: Delaye
authors: Marwan
authors: M
authors: Simaan
authors: Biana
authors: B
authors: Island
authors: Guillaume
authors: G
authors: Eppe
authors: Hendrik
authors: H
authors: Eijsberg
authors: Amir
authors: A
authors: Kleiner
authors: Paul
authors: P
authors: Knochel
authors: Ilan
authors: I
authors: Marek
keywords: carbometalation; chelation; copper; cyclopropene; diastereodivergence