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Light-Induced Chemistry of Oximes and Derivatives

Hydroxylamines, Oximes and Hydroxamic Acids (2010)

  1. Heinz D. Roth

Published Online: 15 SEP 2010

DOI: 10.1002/9780470682531.pat0500

Patai's Chemistry of Functional Groups

Patai's Chemistry of Functional Groups

How to Cite

D. Roth, H. 2010. Light-Induced Chemistry of Oximes and Derivatives. Patai's Chemistry of Functional Groups. .

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Publication History

  1. Published Online: 15 SEP 2010

Abstract

Photoreactions of oximes have been known for 120 years. The earliest recognized reaction was geometric isomerization, which is still the most prominent oxime photoreaction; it proceeds via a ππ* triplet state. More than sixty years later the intriguing photo-Beckmann rearrangement came to light, a C–C=N–O to O=C–N–C conversion, generating, for example, ɛ-caprolactam from cyclohexanone ξιμɛ. The rearrangement proceeds via a ππ* singlet state forming an oxazirane intermediate; the oxazirane ring usually opens in stereospecific fashion. Detailed insight into the stereo- and regiochemistry of the rearrangement was gained from steroidal oximes, the most thoroughly investigated class of oximes.

Additional photoreactions of oximes or of their ethers and esters include: net loss of hydroxylamine generating carbonyl compounds; loss of water from aldoximes forming nitriles; conversion of ketoximes to nitriles by more complex mechanisms; photochemical O–H cleavage generating iminoxyl radicals, an interesting family of free radicals; N–O cleavage giving rise to iminyl radials, which undergo radical cyclizations. β,γ-Unsaturated oximes undergo aza-di-π-methane rearrangements, cyclize to oxazolines, and undergo further reorganizations. The palette of oxime reactions has been further enriched by triplet energy transfer or electron transfer sensitization; oximes serve as electron donors or acceptors.

Keywords:

  • Light-induced chemistry of oximes and derivatives;
  • HEINZ D. ROTH;
  • E, Z isomerization;
  • photo-Beckmann rearrangement;
  • oxazirane formation;
  • O–H cleavage;
  • N–O cleavage;
  • aza-di-π-methane rearrangement;
  • isoxazoline formation;
  • iminoxyl radical;
  • iminyl radial;
  • steroidal oximes;
  • oxo-oximes