Shape-Controlled MoO₃/MnO_x Nanocatalyst for the Selective Synthesis of 2-Phenylquinoxaline Drug Motifs

We have developed a highly effective shape-controlled MoO 3 /MnO x nanocatalyst for the selective synthesis of 2-phenylquinoxaline drug motifs at room temperature without any external oxidant. Electron microscopy images reveal that the MnO x material contains rod-shaped particles (length: 500–1000 nm and width: 150–200 nm) and the MoO 3 species are uniformly dispersed in the MoO 3 /MnO x material. The MoO 3 /MnO x nanocatalyst calcined at 500 °C (MoO 3 /MnO x -5) contains abundant strong acid sites and an optimum ratio of Mn 4+ /Mn 3+, which are responsible for the C–N cross-coupling reaction between 2-phenylethylamine and o-phenylenediamine, giving higher yields (>96%) of 2-phenylquinoxaline at mild conditions. The broad scope of this catalytic strategy at room temperature and without an external oxidant was confirmed by achieving >90% yields of functional 2-phenylquinoxalines from C–N cross-coupling of various o-phenylenediamines and 2-phenylethylamines. The outstanding reusability efficiency of the MoO 3 /MnO x -5 nanocatalyst up to five cycles without the need for a regeneration step as well as the effective scalability highlighted the practicability of the MoO 3 /MnO x -based catalytic protocol for carbon–heteroatom coupling reactions at room temperature and without an external oxidant. Using computational studies, the possible reasons for the selective synthesis of 2-phenylquinoxaline over the MoO 3 /MnO x -5 nanocatalyst were elucidated.