Mixed‐Ligand Mandelato‐Phosphine Copper(I) Complexes as Active Catalysts in Carbene Transfer Reactions

Two mixed ligand copper(I) complexes, [Cu(PPh3)3(k-O-mand)] (CuP3M) and [Cu(PPh3)2(k2-O,O’-mand)] (CuP2M) (mand=dlmandelate) were synthesized and fully characterized. The different coordination modes of the α-hydroxycarboxylate ligand in CuP2M and CuP3M are clearly demonstrated by infrared spectroscopy, with the asymmetric νC=O stretching being observed at 1626 (CuP3M) and 1593 (CuP2M) cm 1, respectively. Solution NMR studies (1H, 31P{1H}), elemental and X-ray structure analyses confirmed the nature of the synthesized
compounds. Complexes CuP2M and CuP3M were in carbene transfer reactions towards unsaturated bonds, using ethyl diazoacetate (N2CHCOOEt, EDA) as carbene source. Indeed, they promoted the trans-diastereoselective cyclopropanation of terminal and internal olefins under mild reaction conditions and low catalyst loading (1% mol).