Nano magnetic double-charged diazoniabicyclo[2.2.2]octane dichloride silica hybrid: Synthesis, characterization, and application as an efficient and reusable organic-inorganic hybrid silica with ionic liquid framework for one-pot synthesis of pyran annulated heterocyclic compounds in water

Organosilane containing bridged double-charged diazoniabicyclo[2.2.2] octane dichloride groups, [(MeO)(3)Si(CH2)(3)N+(CH2CH2)(3)N+(CH2)(3) Si(OME)(3)]Cl-2, was easily prepared and used as a precursor reagent to obtain core shell composite using Fe3O4 spheres and the positively double-charged organic inorganic hybrid silica as the core and shell, respectively. For this reason, the surface of synthesized magnetite nanoparticles by the co-precipitation of FeCl2 and FeCl3, was successfully engineered by deposition of organic inorganic hybrid silica with ionic liquid framework onto nano particles surface using the ammonia-catalyzed hydrolysis of alkoxysilanes groups of organosilane precursor and tetraethylorthosilicate. The magnetic double-charged diazoniabicyclo[2.2.2]octane chloride silica hybrid, Fe3O4@SiO2/DABCO, was characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD) spectroscopy, scanning electron microscope (SEM), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The catalytic activity of the magnetic catalyst was probed through one-pot synthesis of pyran annulated heterocyclic compounds via three-component couplings of aromatic aldehydes, malononitrile and beta-diketone (4-hydroxycoumarin, dimedone and 4-hydroxy-6-methyl-2-pyrone) in water. Due to water-resistant and superparamagnetic nano-nature of Fe3O4@SiO2/DABCO, it could be easily separated by-passing time consuming filtration operation by using an external magnet device and then reused it conveniently. In addition to the facility of this methodology, it also enhances product purity and promises economic as well as environmental benefits. Furthermore, the NMR spectrum of the 2-amino-3-cyano-4-phenyl-8-methylpyrano[3,2-c]pyran-5(4H)-one compound is simulated at HF/6-311++G** level of theory. It is shown that the calculated H-1 and C-13 chemical shifts are in well agreement with the obtained experimental ones. (C) 2013 Elsevier B.V. All rights reserved.