Bidentate carbenoid ester coordination in ruthenium(II) Schiff-base complexes leading to excellent levels of diastereo- and enantioselectivity in catalytic alkene cyclopropanation.

Exceptionally high stereoselectivity (ee < or = 98%, dr < or = 99:1) in the cyclopropanation of alkenes with ethyl diazoacetate using a non-planar ruthenium(II) Schiff-base precatalyst is a result of eta 2C,O binding of the carbenoid ester intermediate, according to DFT calculations.