Enantiospecific Cis-Cyclopropane Synthesis Using the Chiral Iron Carbene Complexes S- and R-(η5-C5H5)(CO)2FeCH[(η6-o-CH3C6H4)Cr(CO)3]+

The first enantiospecific cis-cyclopropanation reaction involving a chiral-at-carbene-ligand complex was developed by utilizing the carbene complex S - or R -Cp(CO) 2 Fe CH[η 6 -( o -CH 3 C 6 H 4 )Cr(CO) 3 ] + ( 6 ). Low-temperature NMR studies indicate that the ratio of syn to anti isomer of the carbene is related to the enantioselectivity of cyclopropanation and lead to the design of 6, which occurs exclusively in the anti conformation.