Abstract
A practical copper-catalyzed aerobic oxidation for the amination of benzoxazole with secondary amine has been discovered. This reaction has proved to be effective to a variety of amines with lower catalyst loading amount, and only oxygen in air is required to facilitate this transformation. A copper-catalyzed/amine-induced ring opening of the benzoxazole and recyclization mechanism was also proposed.
GRAPHICAL ABSTRACT
![](/cms/asset/2e1413a4-c013-4000-9d41-9ab4f66a371e/lsyc_a_919402_o_uf0001.gif)
Notes
a Reaction condition: benzoxazole (0.5 mmol), morpholine (0.6 mmol), catalyst (0.05 mmol), and 2 mL of solvent under air atmosphere for 12 h.
b Isolated yields based on benzoxazole.
c O2 balloon.
d Added 1 mmol benzoic acid.
e Added 1 mmol acetic acid.
f With 5% CuBr2.
a Reaction conditions: benzoxazole (0.5 mmol), amine (0.6 mmol), CuBr2 (0.05 mmol), CH3CN (2 mL), 50 °C, air.
b Isolated yield.
c With 2 eq amine at 50 °C for 30 h.
d With 2 eq amine at 70 °C for 48 h.
e With DMF as nitrogen source.
a Reaction conditions: heteroarene (0.5 mmol), piperdine (0.6 mmol), CuBr2 (0.05 mmol), CH3CN (2 mL), 50 °C, air.
b Isolated yield.
Jia-Ling Wang, Lin-Hui Wang, and Yuan-Yuan Li contributed equally to this work.