Imine‐Linked Porous Organic Polymer Gel and Immobilization of Copper(II): Easy Synthesis and Excellent Catalyst for Huisgen [3+2] Cycloaddition Reactions

Abstract

AbstractPorous organic polymeric gels (POP gels) were made by condensation of a newly synthesized C3‐symmetrical azobenzene‐based tri‐salicylaldehyde building block, 1,3,5‐tris(4‐((3‐formyl‐4‐hydroxyphenyl)diazenyl)phenyl)benzene (TAzo) with suitable aromatic tri‐ and di‐amines in N,N‐dimethylformamide (DMF) at ambient conditions. Here, we have furnished the pathway of an efficient, gentle, and simple one‐pot synthesis of imine‐linked porous organic polymers at room temperature without any acid catalysts. Detail rheological properties of the POP‐gels were studied and were also found to be stable for at least a year at room temperature. Nitrogen isotherm revealed the mesoporous nature of the gel‐powders with moderate surface area. Iminophenol moieties are known to provide binding sites to metallic species via the strong coordination interaction with hydroxy (−OH) and imine (−HC=N−) groups. We have successfully synthesized a copper‐metallated POP by immobilizing copper ions in one of the POP‐gels. The mesoporous POP material having 3 wt % copper loading was utilized for the solvent‐free Huisgen [3+2] cycloaddition reactions of various aryl, benzyl, and alkyl azides with terminal alkynes containing aromatic, heteroaromatic, and alkyl groups with excellent yield. The heterogeneous catalyst with low catalyst loading (1 mol %) was highly regioselective towards 1,4‐disubstituted 1,2,3‐triazoles, recyclable, and did not require the addition of a reducing agent.