Electrochemical Azidooxygenation of Alkenes Mediated by a TEMPO-N3 Charge-Transfer Complex

J Am Chem Soc. 2018 Oct 3;140(39):12511-12520. doi: 10.1021/jacs.8b06744. Epub 2018 Sep 12.

Abstract

We report a mild and efficient electrochemical protocol to access a variety of vicinally C-O and C-N difunctionalized compounds from simple alkenes. Detailed mechanistic studies revealed a distinct reaction pathway from those previously reported for TEMPO-mediated reactions. In this mechanism, electrochemically generated oxoammonium ion facilitates the formation of azidyl radical via a charge-transfer complex with azide, TEMPO-N3. DFT calculations together with spectroscopic characterization provided a tentative structural assignment of this charge-transfer complex. Kinetic and kinetic isotopic effect studies revealed that reversible dissociation of TEMPO-N3 into TEMPO and azidyl precedes the addition of these radicals across the alkene in the rate-determining step. The resulting azidooxygenated product could then be easily manipulated for further synthetic elaborations. The discovery of this new reaction pathway mediated by the TEMPO+/TEMPO redox couple may expand the scope of aminoxyl radical chemistry in synthetic contexts.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Azides / chemistry*
  • Chemistry Techniques, Synthetic
  • Cyclic N-Oxides / chemistry*
  • Electrochemical Techniques
  • Kinetics
  • Spectrophotometry, Ultraviolet

Substances

  • Azides
  • Cyclic N-Oxides
  • TEMPO