Title:The Catalytic Activity of TiO2 Toward a Multicomponent Reaction Depends on its Morphology, Mechanoactivation and Presence of Visible Light
Volume: 1
Author(s): Subramanian Thirumeni, Choumini Balasanthiran and Grigoriy Sereda*
Affiliation:
- Department of Chemistry, University of South Dakota, Vermillion, South Dakota 57069,United States
Keywords:
Visible light, TiO2 nanorods, one-pot multicomponent reaction, solvent free synthesis, 2-amino-4Hbenzo[
b]pyrans, reusable catalyst.
Abstract:
Aims: Test the hypothesis that the catalytic activity of TiO2 nanoparticles towards a liquidphase
or mechanoactivated multicomponent reaction can be tuned by visible light and the shape of
nanoparticles.
Background: Catalytic multicomponent reactions have been proven to be excellent synthetic
approaches to a series of biologically relevant compounds including 2-amino-4H-benzo[b]pyrans.
However, the potential photocatalytic activity and structural diversity of nanostructured catalysts
remained underutilized in the design of new catalytic systems.
Objective: Harness the photocatalytic potential and diverse morphology of TiO2 particles as catalysts
for the liquid phase and mechanoactivated multicomponent organic reactions.
Methods: The multicomponent reactions have been performed under catalytic, photocatalytic, liquid
phase, and mechanoactivated conditions. The catalysts were characterized by XRD and TEM. The
organic reactions products were isolated and characterized by NMR and mass spectroscopy.
Results: Catalytic activity of TiO2 nanoparticles towards multicomponent synthesis of 2-amino-4Hbenzo[
b]pyrans is increased by visible light. The nanorod-shaped TiO2 nanoparticles have shown
substantially higher catalytic activity towards mechanoactivated multicomponent synthesis of 2-
amino-4H-benzo[b]pyrans than their spherically-shaped counterparts.
Conclusion: An efficient methodology for the synthesis of 2-amino-4H-benzo[b]pyrans under
ambient light condition has been developed using TiO2 nanorods (high aspect ratio anatase
nanocrystals) as photocatalyst. This simple method furnished the corresponding terahydrobenzopyrans
in high yields via three component reaction of aldehyde, malononitrile, and dimidone under solvent
free reaction conditions at room temperature. The reaction takes 8-10 min at room temperature under
ambient light condition and the catalyst can be reused multiple times. Utilization of light and the
nanorod morphology of the catalyst through mechanoactivation has been applied for the -first time to
the synthetic technique of multicomponent reactions. The synthetic procedures for 2-amino-4Hbenzo[
b]pyrans have been improved.
