Stereoselective cyclopropanation of unsaturated acetals, using carbohydrates with d-gluco, l-rhamno and d-xylo configurations as chiral auxiliaries

A novel class of tunable cyclopropanation reagents (RXZnCH2Y) and their synthetic applications

The Simmons-Smith cyclopropanation is a widely used method to synthesize cyclopropanes from alkenes using methylene iodide and a zinc reagent. A novel class of organozinc species, RXZnCH(2)Y, has been found to efficiently cyclopropanate alkenes, including traditionally unreactive unfunctionalized alkenes. The reactivity and selectivity of this class of organozinc reagents can be regulated by tuning the electronic and/or steric nature of the RX group attached to Zn. During recent years, this class of organozinc reagent has been widely used in organic synthesis as a reagent for cyclopropanation and other useful synthetic transformations. Catalytic, asymmetric versions of this reaction have been developed providing high enantiomeric excess for unfunctionalized olefins.

New Chiral Sulfonamide Ligands Derived from L-proline for Catalytic Enantioselective Cyclopropanation

Cyclopropanes are important synthetic targets and intermediates. A series of L-proline derivatives as chiral ligands for the cyclopropanation reaction are reported here. The enantioselective cyclopropanation of cinnamyl alcohol has been accomplished with diethyl zinc and diiodomethane in the presence of chiral sulfonamides derived from L-proline and L-proline esters.