A TEMPO-N3 Complex Enables the Electrochemical C-H Azidation of N-Heterocycles through the Cleavage of Alkoxyamines.

Abstract

A TEMPO-N3 charge-transfer complex enables the electrochemical C-H azidation of various N-heterocycles. The TEMPO+ ion, generated from TEMPO, assists in producing N3• by forming a TEMPO-N3 complex with N3-. The formation of this complex is supported by UV-vis absorption spectra, cyclic voltammetry studies, and ESI-HRMS studies. The reaction likely proceeds by forming a highly labile azidooxygenation adduct, which undergoes oxidative alkoxyamine mesolytic cleavage. Subsequent deprotonation of the resulting carbocation exclusively produces the azidation product. It is important to note that substituted olefins generally yield azidooxygenation or diazidation as the final product. Our study demonstrates that N-heterocycles deliver a selective monoazidation product, possibly due to steric reasons. ESI-HRMS studies provide evidence for forming azidooxygenation and alkoxyamine radical cation adducts. The regio- and chemoselectivity of this azidation reaction using the TEMPO-N3 complex have been discussed.