C2-Symmetric fluorous diamines and diimines as ligands for metal-catalysed asymmetric cyclopropanation of styrene

Perfluoroalkyl-substituted, enantiopure C2-symmetric N and N,O ligands showing affinity either for standard organic solvents or perfluorocarbons have been conveniently prepared from readily available precursors. Preformed cobalt(II) and in-situ-generated copper(I) complexes of these ligands were tested as catalysts in the metal-catalysed cyclopropanation of styrene with diazoacetates. Under optimised reaction conditions, which include the use of a fluorous biphasic system and short reaction times, the copper complex of a C2-symmetric diamine afforded promising results (yield = 77%, trans/cis = 67:33, ee of the trans isomer = 62%) and could be easily separated from the products by simply decanting the fluorous phase.