Highly Enantioselective Cyclopropanation of Styrenes with Diazoacetates Catalyzed by Optically Active (beta)Ketoiminato Cobalt(II) Complexes

The highly enantioselective cyclopropanation of styrenes with diazoacetates was achieved using reasonably designed (beta)ketoiminato cobalt(II) complex catalysts. In the presence of optically active cobalt(II) complexes derived from optically active 1,2-(2,4,6-trimethylphenyl)-1,2-ethylenediamine, the cyclopropanation of styrene with methyl, ethyl, and tert-butyl diazoacetates proceeded to afford the corresponding cyclopropanecarboxylates with 94-96% ee.