Two Zn(II)/Cd(II) Coordination Polymers as Recyclable Heterogeneous Catalysts for an Efficient Room-Temperature Synthesis of a-Aminonitriles via the Solvent-Free Strecker Reaction

The alpha-aminonitriles are versatile building blocks in the synthesis of natural or artificial amino acids as well as important intermediates in organic synthesis. For their synthesis, the three component Strecker reaction involving an aldehyde or a ketone together with amines and trimethylsilyl cyanide is used. In the literature, hydrothermally produced metal-based heterogeneous Lewis acid catalysts have been utilized in various solvents. In this work, we aimed at a greener approach toward such catalysis by (a) making two precatalysts with d(10) metal centers, {[Zn(hipamifba)(H2O)]middot2H(2)O}(n )(1) and {[Cd(hipamifba)(H2O)(2)]middot2H(2)O}(n) (2) (where H(2)hipamifba = 4-(((4-((carboxymethyl) carbamoyl)phenyl)amino)methyl)benzoic acid), via an easy and scalable room-temperature method, and (b) showcasing the use of these coordination polymers (CPs) as very efficient, recyclable, and heterogeneous catalysts for the Strecker reaction to form alpha- aminonitriles in high yields under solvent-free reaction at ambient conditions. This has also allowed us to demonstrate the importance of open metal sites in such catalysis through an efficiency comparison between activated 1 and 2. In addition, activated 2 exhibited a wide substrate scope including a natural product Girgensohnine, providing an example of a natural product synthesis by a CP catalyst via an organic transformation such as the Strecker reaction.