Cyclopropane α-Amino Acids via Catalytic Asymmetric Cyclopropanation of Alkenes

Significance

The authors report a nice procedure for the highly diastereoselective and enantio­selective cyclopropanation of alkenes with a copper catalyst. Cyclopropane-containing molecules are found in useful natural and unnatural molecules. The authors used iodosobenzene as a ­reagent to form phenyl iodonium ylides; molecular sieves were used for water scavenging, sodium carbonate as an additive and benzene was the solvent found to be optimal for the reaction. The Cu(I) is important to reach high yields and selectivities, with the SbF₆ ^- counteranion being ideal for desired reactivity. Many various conjugated alkenes gave good yields with excellent selectivity.