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

Abstract

The α-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 d10 metal centers, {[Zn(hipamifba)(H2O)]·2H2O} n (1) and {[Cd(hipamifba)(H2O)2]·2H2O} n (2) (where H2hipamifba = 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 α-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.

Highly Robust Metal–Organic Framework for Efficiently Catalyzing Knoevenagel Condensation and the Strecker Reaction under Solvent-Free Conditions

“…It should be noted that lanthanidebased MOFs often require high reaction times, which is the major drawback to employing them in this direction. 69 Hence, the employment of transition-metal-based MOFs having ample active catalytic sites is on-demand. Furthermore, to validate the heterogeneous catalytic performance of IITKGP-50a, the employed MOF catalyst was removed after 15 min and the reaction was stirred for up to 1 h under the same conditions (Figure S30…”

“…5, Table S7, SI). It should be noted that lanthanide-based MOFs often require high reaction times, which is the major drawback to employing them in this direction . Hence, the employment of transition-metal-based MOFs having ample active catalytic sites is on-demand.…”

A Multivariate 2D Metal–Organic Framework with Open Metal Sites for Catalytic CO2 Cycloaddition and Cyanosilylation Reactions

“…The most desired application of functionalized MOFs is their use as potential heterogeneous catalysts in multicomponent organic transformations. ,, This is because heterogeneous catalysts have gained a lot of popularity over homogeneous catalysts because they can maintain their stability throughout the reaction, can easily be separated from the reaction medium, and can be run for several cycles. An increase in the level of CO 2 , a greenhouse gas, in the atmosphere due to uncontrolled deforestation, industrial growth, and vehicular emission has led to global warming, excessive acidification of water bodies, melting of glacial ice, unpredictable weather changes, and many other serious environmental issues, which require immediate attention.…”