Inverse micelle templated mesoporous manganese oxide (Meso-MnOx) was synthesized by an evaporation induced self-assembly method. Controlled aggregation of manganese oxide nanoparticles, the key to the monomodal mesopores, with tunable structural properties was observed. The material exhibited an excellent catalytic activity in aerobic oxidative coupling of anilines to corresponding azo compounds, due to the presence of its multiple oxidation states and facile transition among them. A variety of aniline derivatives underwent the oxidative homo-coupling and cross-coupling in moderate to excellent yields (as high as 99%). The use of air as the sole oxidant, avoidance of any precious metals and additives, great functional group tolerability, ease of product separation with superior reusability (up to five cycles) and facile but mild reaction condition are the notable features of our catalytic protocol. While investigating the mechanistic details, the involvement of surface-active Mn<sup>3+</sup> species, labile lattice oxygen, and radical intermediates in the catalytic cycle were revealed, which are responsible for the superior catalytic activity. Moreover, a manganese-mediated electron-transfer mechanism from aniline was proposed and was supported by DFT calculations on a computationally modelled complex for the first time.

Mesoporous manganese oxide catalyzed aerobic oxidative coupling of anilines to aromatic azo compounds

253rd National Meeting (2017)

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