A rigid dirhodium(II) carboxylate as an efficient catalyst for the asymmetric cyclopropanation of olefins

The dirhodium(II) complex 7 of (1S,3R,4R)-2-(p-tert-butylphenylsulphonyl)-2-aza-bicyclo[2.2.1]heptane-3-carboxylic acid (3) (or its enantiomer) was synthesised in four steps from cyclopentadiene, (R)- or (S)-phenylethylamine and methyl glyoxylate. Complex 7 was evaluated as a catalyst in the asymmetric cyclopropanation of alkenes with vinyl- and phenyl-diazoesters, resulting in enantioselectivity of up to 92%.