1. Visible light photoredox-controlled reactions of N-radicals
Literature
Report
Visible light photoredox-controlled reactions of N-radicals
Reporter: Leifeng Wang
Prof. Huang Group Meeting
March 21th 2016

2. Contents I: Background
Photocatalyst : What is?
Photocatalyst : What for?
II: Photoredox-controlled reactions of N-radicals
Conversion of N–O and N–S bonds into N-centred radicals
Conversion of N–N bonds into N-centred radicals
Conversion of N–X bonds into N-centred radicals
Conversion of N–H bonds into N-centred radicals
III: Summary

3. Photocatalyst : What is?
In catalysed photolysis, light is absorbed by an adsorbed substrate. In photogenerated catalysis, the photocatalytic activity (PCA) depends on the ability of the catalyst to create electron–hole pairs, which generate free radicals (e.g. hydroxyl radicals: •OH) able to undergo secondary reactions.
Rudolph Marcus Won Nobel Prize
in Chemistry for Marcus Theory of Electron Transfer in 1992. 3

4. Photocatalyst : What is?4
conjugate systerm facilitates electron transfer

5. Photocatalyst : What is?5

6. generation of excited state
Photocatalyst : What For?
photon absorption and
generation of excited state
a short-lived singlet excited state rapidly converts to a long-lived triplet
Juris, A.; Balzani, V. ; Barigelletti, F.; Campagna, S.; Belser, P. ; Von Zelewsky, A. Coord. Chem. Rev. 1988, 84, 85
Damrauer, N. H.; Cerullo, G.; Yeh, A.; Boussie, T. R.; Shank, C. V. ; McCusker, J. K. Science 1997, 275, 54 6

7. Excited State can Relax through a Variety of Pathways
I: Single Electron Transfer (SET)
II: Energy Transfer (ET)
occurs through space (1 – 10 nm)
differences are how substrates are engaged and distance from which transfer occurs
excited photocatalyst has extra energy (1.5 – 3 eV) and can do productive chemistry
occurs through physical contact (< 0.01 nm) 7
Prier, C. K.; Rankic, D. A.;
MacMillan, D. W. C. Chem. Rev , 113, 5322
Scholes, G. D.
Annu. Rev. Phys. Chem. 2003, 54, 57

8. Contents I: Background
Photocatalyst : What is?
Photocatalyst : What for?
II: Photoredox-controlled reactions of N-radicals
Conversion of N–O and N–S bonds into N-centred radicals
Conversion of N–N bonds into N-centred radicals
Conversion of N–X bonds into N-centred radicals
Conversion of N–H bonds into N-centred radicals
III: Summary

9. Contents I: Background
Photocatalyst : What is?
Photocatalyst : What for?
II: Photoredox-controlled reactions of N-radicals
Conversion of N–O and N–S bonds into N-centred radicals
Conversion of N–N bonds into N-centred radicals
Conversion of N–X bonds into N-centred radicals
Conversion of N–H bonds into N-centred radicals
III: Summary

10. Conversion of N–O bond Proposed mechanism MacMillan Group 10
We report herein a visible light induced generation of a carbanion
via double-SET and its application in cyclopropanation of alkenes.
This new synthetic approach to form cyclopropane derivatives
was conducted under mild conditions, using sunlight in open air,
showing the features such as environmental benignness and an
easy to handle procedure.
Proposed
mechanism
MacMillan Group 10
J. Am. Chem. Soc. 2013, 135, 11521

11. Conversion of N–O bond Proposed mechanism Sanford group 11
J. Am. Chem. Soc. 2014, 136, 5607
Chem. Soc., 2014, 136, 5607

12. Conversion of N–O bond
S.-Y. Yu group
Org. Lett. 2014, 16, 3504 12

13. Conversion of N–O bond S.-Y. Yu group
Angew. Chem. Int. Ed. 2015, 54, 4055 13

14. Conversion of N–O bond S.-Y. Yu group
Angew. Chem. Int. Ed. 2015, 54, 4055 14

15. Conversion of N–O bond Leonori group
Angew. Chem. Int. Ed. 2015, 54, 14017 15

16. Conversion of N–S bond W.-J. Xiao group Chem. – Asian J. 2013, 8, 109016

17. Contents I: Background
Photocatalyst : What is?
Photocatalyst : What for?
II: Photoredox-controlled reactions of N-radicals
Conversion of N–O and N–S bonds into N-centred radicals
Conversion of N–N bonds into N-centred radicals
Conversion of N–X bonds into N-centred radicals
Conversion of N–H bonds into N-centred radicals
III: Summary

18. Conversion of N–N bond
Studer group
Org. Lett. 2014, 16, 254 17

19. Conversion of N–N bond
Studer group
Org. Lett. 2014, 16, 254 18

20. Conversion of N–N bond
Akita group
Chem. – Eur. J. 2015, 21, 11677 20

21. Conversion of N–N bond
Liu group
Nat. Chem. 2011, 3, 146 21

22. Contents I: Background
Photocatalyst : What is?
Photocatalyst : What for?
II: Photoredox-controlled reactions of N-radicals
Conversion of N–O and N–S bonds into N-centred radicals
Conversion of N–N bonds into N-centred radicals
Conversion of N–X bonds into N-centred radicals
Conversion of N–H bonds into N-centred radicals
III: Summary

23. Conversion of N–X bond Lee Group Chem.Commun. 2014, 50, 9273 Xue Group
Synlett. 2014, 22

24. Conversion of N–X bond S.-Y. Yu group Org. Lett. 2015, 17, 1894
Org. Biomol. Chem. 2015, 13, 10295 23

25. Conversion of N–X bond
S.-Y. Yu group
Org. Lett. 2015, 17, 1894 23

26. Contents I: Background
Photocatalyst : What is?
Photocatalyst : What for?
II: Photoredox-controlled reactions of N-radicals
Conversion of N–O and N–S bonds into N-centred radicals
Conversion of N–N bonds into N-centred radicals
Conversion of N–X bonds into N-centred radicals
Conversion of N–H bonds into N-centred radicals
III: Summary

27. Conversion of N–H bond 24
W.-J. Xiao group Angew. Chem. Int. Ed. 2015, 54, 14017

28. Conversion of N–H bond Knowles Group J. Am. Chem. Soc. 2015, 137, 922625

29. Contents I: Background
Photocatalyst : What is?
Photocatalyst : What for?
II: Photoredox-controlled reactions of N-radicals
Conversion of N–O and N–S bonds into N-centred radicals
Conversion of N–N bonds into N-centred radicals
Conversion of N–X bonds into N-centred radicals
Conversion of N–H bonds into N-centred radicals
III: Summary

30. Summary Challenges Remain:
1) the activation of other more challenging N–H bonds and exploration of new reaction modes
2) the asymmetric variants of N-radicals and radical ion-mediated reactions

31. Thank You for Your kind attention!