University of Washington
Obenschain, Derek Curtis.
Alkene Amination Reactions Enabled by Organoselenium Catalysis.
Degree: PhD, 2021, University of Washington
The discovery of new modes of catalytic reactivity represents the forefront of organic methodology. Many important transformations are catalyzed by expensive transition metal catalysts. Replacing these with cheaper, more abundant alternatives is an important goal. This dissertation explores the development of new catalytic oxidative transformations enabled by organoselenium catalysts. The focus of this work is on using these organoselenium catalysts to enable a variety of amination reactions.Herein, the development of three oxidative allylic C-H amination reactions enabled by novel organoselenium catalysis is presented: the allylic C-H amination of alkenes using sulfonamides, the expansion of this transformation to utilize carbamates and trifluoroacetamide as nucleophiles, and the direct formation of conjugated sulfonyl imines from alkenes. The development of a 1,2-diamination of alkenes using these same organoselenium catalysts is also discussed.
A novel selenium-catalyzed C-H amination reaction was achieved using either phosphine or imidazolium-based ligands on selenium with diacetoxyiodobenzene as an oxidant and sulfonamides serving as the amine sources. This transformation enabled amination for all alkene substitution patterns with a highly predictable regiochemical outcome. An extensive number of functional groups were tolerated by these reaction conditions and numerous synthetically valuable sulfonamide and sulfamate nucleophiles were found to be suitable coupling partners for this reaction. Pharmaceutical drugs, natural products, and terpenoids were derivatized using this method demonstrating its power for late-stage functionalization.
A direct protocol for the synthesis of conjugated sulfonyl imines from highly substituted alkenes was also developed. This reaction was realized by increasing the oxidizing power of the amination reaction conditions and through the careful optimization of the catalyst and sulfonamide coupling partner. The use of the triarylphosphine selenide catalysts were critical in the development of this reaction by suppressing a competitive diamination reaction. The use of electron rich sulfonamides was found to be important for high yields of the desired imine products. Various novel derivatizations of the imine products were developed including a transimination protocol.
An expansion of the selenium-catalyzed C-H amination reaction described above to incorporate carbamate nucleophiles was also realized. The use of N-tert-butyl imidazolium ligand on selenium proved critical in enabling good yields for this transformation. Numerous synthetically valuable carbamate nucleophiles including benzyl, allyl, and trimethylsilyl ethyl carbamates were found to be competent coupling partners in this reaction. The transformation was successful for a variety of 1,1-di- and tri-substituted olefins offering unprecedented direct access to allylic carbamates through catalytic C-H activation. Trifluoroacetamide was also shown to be a suitable coupling partner for this reaction. The late…
Advisors/Committee Members: Michael, Forrest E (advisor).
to Zotero / EndNote / Reference
APA (6th Edition):
Obenschain, D. C. (2021). Alkene Amination Reactions Enabled by Organoselenium Catalysis. (Doctoral Dissertation). University of Washington. Retrieved from http://hdl.handle.net/1773/46753
Chicago Manual of Style (16th Edition):
Obenschain, Derek Curtis. “Alkene Amination Reactions Enabled by Organoselenium Catalysis.” 2021. Doctoral Dissertation, University of Washington. Accessed April 22, 2021.
MLA Handbook (7th Edition):
Obenschain, Derek Curtis. “Alkene Amination Reactions Enabled by Organoselenium Catalysis.” 2021. Web. 22 Apr 2021.
Obenschain DC. Alkene Amination Reactions Enabled by Organoselenium Catalysis. [Internet] [Doctoral dissertation]. University of Washington; 2021. [cited 2021 Apr 22].
Available from: http://hdl.handle.net/1773/46753.
Council of Science Editors:
Obenschain DC. Alkene Amination Reactions Enabled by Organoselenium Catalysis. [Doctoral Dissertation]. University of Washington; 2021. Available from: http://hdl.handle.net/1773/46753