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

Three new compounds bearing different flexible side functional groups, viz. 2-acetamidoterephthalic acid (H(2)L1), 2-propionamidoterephthalic acid (H(2)L2) and 2-benzamidoterephthalic acid (H(2)L3), 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 [Zn-2(L1)(2)(4,4'-bipyridine) (2)(H2O)(DMF)](n) (1), [Zn-4(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.