Zinc metal–organic frameworks: efficient catalysts for the diastereoselective Henry reaction and transesterification

Abstract

Three new compounds bearing different flexible side functional groups, viz. 2-acetamidoterephthalic acid (H₂L1), 2-propionamidoterephthalic acid (H₂L2) and 2-benzamidoterephthalic acid (H₂L3), were synthesized and their coordination reactions with zinc(II) were studied. X-ray crystallography showed the formation of novel metal organic frameworks with different dimensionalities, where the side functional groups of amidoterephthalic acid and/or auxiliary ligands were found to play significant roles. These frameworks [Zn₂(L1)₂(4,4′-bipyridine)₂(H₂O)(DMF)]_n (1), [Zn₄(L2)₃(OH)₂(DMF)₂(H₂O)₂]_n (2) and [Zn(L3)(H₂O)₂]_n·n/2(1,4-dioxane) (3) act as heterogeneous polymeric solid catalysts not only for the diastereoselective nitroaldol (Henry) reaction of different aldehydes with nitroalkanes but also for transesterification reactions. These MOF-based heterogeneous catalysts can be recycled without losing their activity.