title: Magnetite Nanoparticles-Supported APTES as a Powerful and Recoverable Nanocatalyst for the Preparation of 2-Amino-5,10-dihydro- 5,10-dioxo-4H-benzo[g]chromenes and Tetrahydrobenzo[g]quinoline-5,10- diones.
abstract: OBJECTIVE
  This study introduces a green and effective approach for the preparation of biologically-active heterocyclic compounds including 2-amino-5,10-dihydro-5,10-dioxo-4Hbenzo[ g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones using one-pot multi-component reactions in the presence of Fe3O4@SiO2-NH2 nanocomposite. The preparation and use of aminofunctionalized Fe3O4@SiO2 as a powerful and reusable nanocatalyst is described. The catalyst was characterized by spectral techniques including FT-IR, SEM, XRD, EDX and VSM analysis. This method offers the advantages of high yields, short reaction times, comfortable work-up and reusability of the catalyst.
  
  
  METHODS
  The amino-functionalization silica-coated magnetite nanocomposite was prepared by three step method and the structure elucidation of the nanocatalyst has been done using various spectroscopic analyses. Then, the Fe3O4@SiO2-NH2 nanocomposite was used in the multicomponent synthesis of 2-amino-5,10-dihydro-5,10-dioxo-4H-benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones under reflux conditions. All of the products were analyzed with m.p., 1H NMR, 13C NMR and FT-IR spectroscopy techniques. The study on the recoverability of the nanocatalyst showed the recovered Fe3O4@SiO2-NH2 nanocomposite could be reused sixth consecutive times with a little-decreased activity.
  
  
  RESULTS
  Amino-functionalized SiO2 coated Fe3O4 nanocomposite exhibited superparamagnetic behavior and strong magnetization at room temperature. The average crystallite sizes of the catalyst was about 50-60 nm. The obtained magnetic nanocomposite showed excellent catalytic activity as a new heterogeneous magnetic catalyst for the synthesis of some benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones. We propose that NH2 groups on the surfaces of nanocomposite act as the Brønsted base and cause to dehydrogenation of substrates to promote the reactions.
  
  
  CONCLUSIONS
  It was found that Fe3O4@SiO2-NH2 nanocomposite act as an eco-friendly and efficient catalyst for one-pot synthesis of three/four component condensation reactions. In this research, aminofunctionalized Fe3O4@SiO2 was used as recoverable catalyst for the synthesis of 2-amino-5,10- dihydro-5,10-dioxo-4H-benzo[g]chromenes and tetrahydrobenzo[g]quinoline-5,10-diones under reflux conditions. The significant advantages of this method are the reasonably simple work-up, little catalyst loading, short reaction times, excellent yields, non-hygroscopic quality and reusability of the nanocatalyst which is in good agreement with green chemistry disciplines.
authors.affiliation: Department of Chemistry, Qom Branch, Islamic Azad University, Qom, I.R.. Iran.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Ghasemzadeh
authors.forename: Zahra
authors.initials: Z
authors.lastname: Elyasi
authors.forename: Mina
authors.initials: M
authors.lastname: Azimi-Nasrabad
authors.forename: Boshra
authors.initials: B
authors.lastname: Mirhosseini-Eshkevari
mesh_terms: D000586:Amination; D001555:Benzene Derivatives / Q000138:chemical synthesis* / Q000737:chemistry; D001578:Benzopyrans / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques / Q000379:methods; D055772:Green Chemistry Technology / Q000379:methods; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D011804:Quinolines / Q000138:chemical synthesis* / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D001555:Benzene Derivatives; D001578:Benzopyrans; D058185:Magnetite Nanoparticles; D011804:Quinolines; D012822:Silicon Dioxide
keywords: 10-dione; Fe3O4@SiO2-NH2; benzo[g]chromene; core–shell; multi-component reaction; nanocomposite; tetrahydrobenzo[g]
  quinoline-5