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Can singlet oxygen facilitate a (2+2) cycloaddition reaction, for example between two alkenes, by reacting first with the pi-electrons in one alkene and then lowering the energy barrier for the second alkene to attack (given the instability of 1,2-dioxetane)? Are there any examples of this sort of thing?

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I'm not aware of any such examples. In the reactions of singlet oxygen with olefins only products from cycloaddition to form a dioxetane and \ or products from the ene reaction are observed. There are no reports of olefin dimerization.

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  • $\begingroup$ I read through this paper (Harding & Goddard JACS 102(2), 1980): pubs.acs.org/doi/pdf/10.1021/ja00522a001, and it isn't really clear to me what happens if we frustrate the ene reaction by not having a carbon to deprotonate adjacent to the attack site of the oxygen radical? $\endgroup$ – user5486 May 13 '14 at 17:15
  • $\begingroup$ That should enhance the dioxetane formation pathway. $\endgroup$ – ron May 13 '14 at 17:42
  • $\begingroup$ Right, I was wondering if perhaps the reason there are no reports for dimerization have to do with fast intramolecular resolution of some unstable dioxetane intermediate. Perhaps stabilizing this intermediate would allow for some kind of dimerization? $\endgroup$ – user5486 May 13 '14 at 18:05

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