TEMPO-Mediated C-H Amination of Benzoxazoles with N-Heterocycles.

The direct amination of benzoxazoles at C2 using N-heterocycles as nitrogen sources has been developed for the first time. Several kinds of inexpensive oxidants and also electricity were effective for this transformation in the presence of 2,2,6,6-tetramethylpiperidine-N-oxyl. This metal-free and operationally simple reaction can afford a variety of important C,N'-linked bis-heteocycles in moderate to good yields under very mild reaction conditions. The in situ generated oxoammonium salt was proved to be important for this transformation.