Synthesis of the organic–inorganic hybrid catalyst via covalently anchored basic organomoieties on to the SBA-15: a recyclable catalyst for the preparation of chromene derivatives in water

In this work, for the first time, SBA supported homogeneous basic catalyst (piperazine–ethyl urea) was synthesized via a simple and convenient method. Briefly, the active homogeneous catalyst is chemically immobilized onto the SBA through silylation of hydroxyl groups to form heterogeneous catalyst that contains basic moieties. The formation of this catalyst was confirmed by elemental analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction spectroscopy, thermal gravimetric analysis and Brunauer Emmett Teller. All of the characterization methods revealed that basic moieties were conveniently immobilized on to SBA as support. Therefore, it provides a novel heterogeneous basic catalyst for achieving synthetic goals. The immobilized basic catalyst provides a green and useful method for one-pot synthesis of chromene derivatives by multicomponent condensation of 4-hydroxycoumarin, 4-chlorobenzaldehyde and malononitrile. The promising points for the presented methodology are clean reaction profiles, short reaction times, simplicity in operation, catalyst with high catalytic activity and good recycle exploitation.