Bergman cyclization
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The Bergman cyclization or Bergman reaction or Bergman cycloaromatization is an organic reaction and more specifically a rearrangement reaction taking place when an enyne is heated in presence of a suitable hydrogen donor (Scheme 1). The reaction product is a derivative of benzene.
The reaction proceeds by a thermal reaction or pyrolysis (above 200°C) forming a short-lived and very reactive para-benzyne diradical species. It will react with any hydrogen donor such as 1,4-cyclohexadiene which converts to benzene. When quenched by tetrachloromethane the reaction product is a 1,4-dichlorobenzene and with methanol the reaction product is benzyl alcohol.
When the enyne moiety is incorporated into a 10-membered hydrocarbon ring (e.g. cyclodeca-3-ene-1,5-diyne in scheme 2) the reaction, taking advantage of increased ring strain in the reactant, is possible at the much lower temperature of 37°C.
Naturally occurring compounds exist containing the same 10-membered enyne ring and are found to be cytotoxic. These compounds generate the diradical intermediate described above which cause single- and double stranded DNA cuts. Novel drug research attempts to make use of this property .
[edit] External links
- Bergman Cycloaromatization Powerpoint Whitney M. Erwin 2002
[edit] References
- ↑ p-Benzyne. Generation as an intermediate in a thermal isomerization reaction and trapping evidence for the 1,4-benzenediyl structure Richard R. Jones, Robert G. Bergman J. Am. Chem. Soc.; 1972; 94(2); 660-661. Abstract
- ↑ Design and synthesis of heterocycle fused enediyne prodrugs activable at willLuca Banfi, Andrea Basso, Giuseppe Guanti, and Renata Riva Arkivoc 2006 HL-1786GR 261-275 Abstract
