4. Photogeneration of Biradicals and Radical Pairs

  1. Angelo Albini and
  2. Maurizio Fagnoni

Published Online: 12 JUL 2013

DOI: 10.1002/9781118689202.ch04

Photochemically-Generated Intermediates In Synthesis

Photochemically-Generated Intermediates In Synthesis

How to Cite

Albini, A. and Fagnoni, M. (eds) (2013) Photogeneration of Biradicals and Radical Pairs, in Photochemically-Generated Intermediates In Synthesis, John Wiley & Sons, Inc., Hoboken, New Jersey. doi: 10.1002/9781118689202.ch04

Editor Information

  1. PhotoGreen Lab, Department of Chemistry, University of Pavia, Pavia, Italy

Publication History

  1. Published Online: 12 JUL 2013
  2. Published Print: 23 AUG 2013

ISBN Information

Print ISBN: 9780470915349

Online ISBN: 9781118689202



  • aromatic biradicals;
  • cyclic compounds;
  • open-chain compounds;
  • photogeneration;
  • photoinduced ring opening


An important group of reactions that intrinsically produce aromatic biradicals involves the cycloaromatization of highly unsaturated hydrocarbons, as in the Bergman and the Myers-Saito reactions. The reactions presented in this chapter are, for a large part, based on the rich photochemistry of the carbonyl moiety-in particular, on the generation of a biradical by a Norrish type I or type II reaction. In all of the processes, a ring is formed by radical—radical coupling from photogenerated biradicals. The chapter describes the formation of various rings, namely, three-, four-, five-, and six-membered rings. It then focuses on synthesis of open-chain compounds, and finally discusses the role of aromatic biradical intermediates, such as o-benzynes, p-benzynes, and α,n-didehydrotoluenes, albeit their application in synthesis has been scarcely documented.