Chemical Society Seminar: Armido Studer - Electron Catalysis

Event

Maass Chemistry Building Room 10, 801 rue Sherbrooke Ouest, Montreal, QC, H3A 0B8, CA

Radical reactions are routinely considered in synthetic planning, and highly active research continues on new ways to make and use radicals. Because the products of radical-molecule reactions are again radicals, such processes are perfectly suited to be run as sequential reactions (cascades). Likewise, because radicals can be oxidized or reduced, radical-ionic crossover reactions can be implemented. Such cascade reactions serve well the goal of step economy in organic synthesis. As compared to non-radical processes, most radical reactions are very fast. Radical chain reactions require only a small amount of an initiator and addition of a catalyst is generally not necessary. Therefore, it is often difficult to catalyze radical transformations since background chain reactions are so fast.[1]

In the lecture the concept of using the electron as a catalyst will be discussed.[1,2] It will be shown that the electron is an efficient catalyst for conducting various types of radical cascade reactions that proceed via radical and radical ion intermediates. The “electron is a catalyst” paradigm unifies mechanistically an assortment of synthetic transformations that otherwise have little or no apparent relationship. Some recent examples on the use of the electron as a catalyst will be discussed.[3]

It will be emphasized how a negative charge can significantly weaken the neighbouring C-H bond and activate this bond towards H-atom transfer.[3e,j] Moreover, the activation of a C-H bond next to a C-radical towards deprotonation is a key point in the field of electron-catalysis. This issue will be addressed in the lecture. Extending that concept, the use of a negative charge to activate a C-C sigma-bond towards homolysis is also discussed.[3i,k] For example, electron catalyzed transition metal-free b-alkenylation-a-perfluoroalkylation of unactivated alkenes via radical 1,4 or 1,5-alkenyl migration will be presented. Electrochemistry can be applied to initiate electron-catalyzed processes.[3m]

It will be further shown, that readily generated vinyl boron ate complexes, generally used as substrates in the Suzuki-Miyaura coupling, are efficient radical acceptors to conduct electron-catalyzed modular synthesis comprising a radical polar cross over step.[3h] This approach has recently been successfully applied to the development of a novel method for the preparation of highly enantioenriched a-chiral ketones[3l] and a new method for radical borylation is discussed.[3n]

References

[1] A. Studer, D. P. Curran, Angew. Chem. Int. Ed. 2016, 55, 58-102.
[2] A. Studer, D. P. Curran, Nature Chem. 2014, 6, 765-773.
[3] (a) B. Zhang, A. Studer, Org. Lett. 2014, 16, 3990-3993. (b) D. Leifert, A Studer, Org. Lett. 2015, 17, 386-389. (c) M. Hartmann, C. G. Daniliuc, A. Studer, Chem. Commun. 2015, 51, 3121-3123. (d) D. Leifert, D. G. Artiukhin, J. Neugebauer, A. Galstyan, C. A. Strassert, A. Studer, Chem. Commun. 2016, 52, 5997-6000. (e) A. Dewanji, C. Mück-Lichtenfeld, A. Studer, Angew. Chem. Int. Ed. 2016, 55, 6749-6752. (f) J. Xuan, C. G. Daniliuc, A. Studer, Org. Lett. 2016, 18, 6372–6375. (h) M. Kischkewitz, K. Okamoto, C. Mück-Lichtenfeld, A. Studer, Science 2017, 355, 936-938. (i) X. Tang, A. Studer, Chem. Sci. 2017, 8, 6888-6892. (j) T. Hokamp, A. Dewanji, M. Lübbesmeyer, C. Mück-Lichtenfeld, E.-U. Würthwein, A. Studer, Angew. Chem. Int. Ed. 2017, 56, 13275-13278. (k) X. Tang, A. Studer, Angew. Chem. Int. Ed. 2018, 57, 814-817. (l) C. Gerleve, M. Kischkewitz, A. Studer, Angew. Chem. Int. Ed. 2018, 57, 2441-2444. (m) M. Lübbesmeyer, D. Leifert, H. Schäfer, A. Studer, Chem. Commun. 2018, 54, 2240-2243. (n) Y. Cheng, C. Mück-Lichtenfeld, A. Studer, J. Am. Chem. Soc. 2018, 140, 6221-6225.

Contact Information

Contact: 
CJ Li
Email: 
CJ.Li [at] McGill.ca