Asymmetric cyclopropanation of olefins catalyzed by chiral cobalt(II)-binaphthyl porphyrins

Cobalt(II) complexes of chiral bis-binaphthyl porphyrins were prepared, and their catalytic activity in the asymmetric cyclopropanation of alkenes with ethyl diazoacetate was examined. Good yields and enantioselectivities (up to 90% ee) were observed with cis/trans ratios reaching 11:89. UV-vis and 1H NMR studies suggest that the axial nitrogen ligand N-methylimidazole could play a role in changing the enantioselectivity of the reaction.