Highly enantioselective cyclopropanation of styrenes with diazoacetates catalyzed by optically active β-ketoiminato cobalt(II) complexes

The highly enantioselective cyclopropanation of styrenes with diazoacetates was achieved using reasonably designed β-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.