CuI complexes containing a multidentate and conformationally flexible dibenzylidene acetone ligand (dbathiophos): Application in catalytic alkene cyclopropanation

The synthesis and characterisation of a multidentate conformationally flexible ligand based on the dibenzylidene acetone core structure, dbathiophos (1), is described. Ligand 1 has a high affinity for cationic and neutral CuI species. Three unique CuI complexes (4–6) are reported showing that the ligand backbone of dbathiophos is hemilabile, and able to adopt different 1,4-dien-3-one conformational geometries around CuI. Complexes 4 and 6 both effectively catalyse the cyclopropanation of styrene with ethyl diazoacetate at low catalyst loadings (1 mol% Cu).