3
$\begingroup$

I've recently come across a couple examples of intramolecular alkene hydroamination accomplished by treatment with LDA followed by visible light irradiation (tungsten light bulb):[1,2]

Examples of intramolecular hydroamination

I'd assume that this proceeds via some kind of radical mechanism, with the initially formed amide ion losing one electron to form an aminyl radical which then adds into the alkene. Trost[2] also suggests that the addition is facilitated by an SET:

Possible mechanism

My question is – what species is taking the electron away, and how is that species generated? There doesn't seem to be any decent electron acceptor in this system, unlike, for example, Ru(II) in a photoredox mechanism. If one is aware of any mechanistic studies which have been carried out, it would be an added bonus.


References

  1. Kou, K. G. M.; Pflueger, J. J.; Kiho, T.; Morrill, L. C.; Fisher, E. L.; Clagg, K.; Lebold, T. P.; Kisunzu, J. K.; Sarpong, R. A Benzyne Insertion Approach to Hetisine-Type Diterpenoid Alkaloids: Synthesis of Cossonidine (Davisine). J. Am. Chem. Soc. 2018, 140 (26), 8105–8109. DOI: 10.1021/jacs.8b05043.
  2. Trost, B. M.; Tang, W. Enantioselective Synthesis of (−)-Codeine and (−)-Morphine. J. Am. Chem. Soc. 2002, 124 (49), 14542–14543. DOI: 10.1021/ja0283394.
$\endgroup$
  • $\begingroup$ Why not email the starred author of the first paper you reference and ask them? $\endgroup$ – Waylander Aug 15 '18 at 10:01
  • $\begingroup$ I can't read the whole thing, but there is this review on hydroamination: pubs.acs.org/doi/10.1021/cr0306788 $\endgroup$ – Zhe Aug 15 '18 at 13:22
  • $\begingroup$ It just occurred to me. I wonder if the aryl ring in the substrate is actually serving as a chromophore... $\endgroup$ – Zhe Aug 15 '18 at 13:25
  • $\begingroup$ Also, according to this reference, reference (2) has some reproducibility issues: iupac.org/publications/pac/pdf/2010/pdf/8209x1785.pdf $\endgroup$ – Zhe Aug 15 '18 at 13:28
  • $\begingroup$ One more question, how many equivalents of LDA are used? $\endgroup$ – Zhe Aug 15 '18 at 15:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.