Ball-milling synthesized hydrotalcite supported Cu–Mn mixed oxide under solvent-free conditions: an active catalyst for aerobic oxidative synthesis of 2-acylbenzothiazoles and quinoxalines†
A rapid solvent-free ball-milling method was developed to prepare a hydrophobic hydrotalcite supported Cu–Mn mixed oxide catalyst (Cu–Mn/HT). The mechanochemically prepared catalyst exhibited high catalytic activity and recyclability towards the aerobic synthesis of 2-acylbenzothiazoles and quinoxalines in green medium ethanol compared with the ones synthesized via grinding and wet-impregnation. Moreover, control experiments showed that the catalyst was successfully used in green oxidative esterification and coupling as well. Cu–Mn/HT was characterized by BET, ICP, XRD, XPS, SEM and TEM, which indicated that more surface oxygen vacancies and formed CuMn2O4 species on HT might contribute to the catalytic activity.