Diastereoselective Nitroaldol Reaction Catalyzed by Binuclear Copper(II) Complexes in Aqueous Medium

Abstract

Abstract Polydentate ligands 1 and 2 , which incorporate a terminal pyridyl moiety and an oxygen‐rich oxalate dihydrizide/malonic dihydrizide spacer moiety, as well as their binuclear metal complexes [Cu 2 1 2 ] and [Cu 2 2 2 ], which adopt a 1:1 metal/ligand ratio, were synthesized and characterized. Both complexes were screened for their catalytic activity in the nitroaldol reaction, in which [Cu 2 1 2 ] worked efficiently as catalyst for both substituted benzaldehyde and pyridinecarboxaldehyde, whereas [Cu 2 2 2 ] is highly substrate specific and showed activity towards nitro‐substituted aldehydes and pyridinecarboxaldehyde. Furthermore, as helicates are intrinsically chiral, the stereochemical architecture in the binuclear double‐stranded Cu 2 helicates as catalyst favored the diastereoselective syn product with nitroethane and nitropropane and their respective diastereoselectivities were determined by using 1 H NMR spectroscopy.