CATALYTIC ASYMMETRIC CARBOZINCATION OF CYCLOPROPENES

The asymmetric carbozincation of cyclopropenes represents an attractive alternative for the synthesis of
enantioenriched cyclopropanes. In particular the synthesis of unfunctionalized enantioenriched cyclopropanes
requires a multi-step synthesis and is limited in the choice of substituents on the cyclopropane ring. We recently
found that unfunctionalized cyclopropenes in the presence of a chiral copper catalyst react smoothly with
organometallic reagents such as diorganozinc reagents to furnish highly substituted enantioenriched cyclopropyl
zinc reagents in high yield and excellent enantioselectivity (>99% er). Moreover, we demonstrate the synthetic
use of the corresponding cyclopropylmetals for a great variety of subsequent reactions such as allylic
substitutions, 1,4-addition, coupling reactions and many others. This unprecedented synthesis of cyclopropanes
is also very practical proceeding efficiently with low catalyst loading (>0.5 mol%) and mild reaction conditions.