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.

Asymmetric catalysis provides outstanding tools to introduce chiral information to a substrate by using only catalytic amounts of a chiral transition-metal complex.[1] The success of these efficient asymmetric processes relies on the development of chiral ligands that form a complex with the metal; until very recently phosphorus-, nitrogen-, and oxygen-containing chiral ligands were the only ones available. Recently, the groups of Hayashi and Carreira independently reported the use of chiral dienes in asymmetric catalysis: [2] high levels of enantioselectivity were achieved in both the iridiumcatalyzed kinetic resolution of allyl carbonates [3] and the rhodium-catalyzed 1,4-additions of organoboron reagents to Michael acceptors. [4,5]

An overview of the most important synthetic strategies currently available for the preparation of cyclopent-2-enones is presented and illustrated with recent applications.