Selective synthesis of 2-amino-3H-phenoxazin-3-one on titanium oxide supported bimetallic Ru-Au and Ru-Pd nanocatalysts Thandiwe Mntambo 1 , Mabuatsela V. Maphoru 1 , Letlhogonolo F Mabena 1 , Mzamo Shozi 2 1 Tshwane University of Technology, South Africa, 2 University of KwaZulu-Natal, South Africa Aminoquinones and phenoxazinones are vital molecules in pharmaceutical and medicinal industries due to their biological activeness [1]. Recent developments in their sustainable synthesis are exploring heterogeneous catalytic methods that include the use of active noble metals supported on metal oxides as catalysts and clean oxidants like hydrogen peroxide [2]. This type of catalysts are of great interest since they can be easily separated from the products and be recycled without significant loss of their catalytic activities [2]. In this study, titania supported Ru-Au and Ru-Pd nanocatalysts were synthesized by the microwave-polyol assisted method. A combination of XRD, SEM, SEM-EDX, and TEM was used to characterize the synthesized bimetallic catalysts. The TEM micrograph of 1%Ru-1%Pd/TiO 2 catalyst showed the presence of metal NPs homogenously dispersed on the support surface (Figure 1, attached) and their identity was further confirmed by EDX analysis. Their catalytic behavior was tested in the oxidation of 2-aminophenol to 2-amino-3 H -phenoxazin-3-one (APX), in different solvents at room temperature and under reflux (Scheme 1, attached). It was observed that the catalysts’ activities and selectivities highly depend on the type of solvent and catalyst, as well as temperature used. A yield of 94% ( 2 ) was obtained when using Ru-Pd catalyst in methanol at room temperature in comparison to 54% obtained on Ru-Au under the same reaction conditions. However, Ru-Au showed a significant catalytic activity when methanol was replaced with nitromethane, where a yield of 68% for APX was obtained. Low catalytic activities were realized for both Ru-Pd and Ru-Au catalysts in acetonitrile under the same reaction conditions.
References 1. El-Najjar, N.; Gali-Muhtasib, H.; Ketola, R.A.; Vuorela, P.; Urtti, A.; Vuorela, H. Phytochem. Rev. , 2011, 10: 353-370. 2. Gualteros J.A.D.; Garcia, M.A.S.; Da-Silva, A.G.M.; Rodrigues, T.S.; Candido, E.G.; Silva, F.A.E. J. Mater.Sci. , 2019, 54:238- 251.
P72
© The Author(s), 2022
Made with FlippingBook Learn more on our blog