Date of Graduation

8-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor/Mentor

Nan Zheng

Committee Member

Matthias McIntosh

Second Committee Member

Bill Durham

Third Committee Member

Jingyi Chen

Keywords

[4+2] Annulation, Cyclobutylaniline, Photoredox Catalysis, Visible Light

Abstract

While transition metal catalyzed cross coupling reactions have become one of the most useful strategies in constructing carbon-carbon and carbon-heteroatom bond formations, major disadvantages such as high reaction temperature, expansive metal catalysts input and limited reaction substrates scope have significantly downshifted the applications of those two electron involved transformations. Comparably, the studies on the redox coupling reactions are less investigated. Derived from single electron transfer process, the redox coupling reactions can be used to construct otherwise challenging chemical bonds efficiently, such as Csp3-Csp3 bond. Recently, visible light mediated photoredox catalysis has merged as a highly prominent tool in the development of many unconventional organic transformations. Those transformations are typically conducted in an extremely mild reaction conditions only by irradiating reaction mixtures under visible light or sunshine at room temperature and without any ligand addition. Hence, exceptional efforts are needed for further exploration of those photoredox catalyzed organic transformations. This work described an innovation approach of using visible light photoredox catalysis to develop efficient one-step syntheses for the construction of structurally diverse amine substituted novel cyclic and acyclic organic motifs from easily prepared starting materials.

Amines are typically used as a sacrificial electron donor in a photoredox derived reaction. Nan Zheng recently revealed that by incorporating amine into a reductive quenching photoredox catalytic cycle, amine can be used as both the sacrificial electron donor and substrate. To accomplish this, N-cyclobutylanilines were oxidized to its corresponding amine radical cation by a photoredox catalyst upon irradiation under visible light, which would lead to a distonic radical cation through a C-C bond cleavage of cyclobutyl ring. The distonic radical cation can be trapped by a pi bond such as alkene or alkyne to reveal a novel amine substituted six membered carbon cycle through a [4+2] annulation reaction. Alternatively, by introducing a nucleophile such as trimethylsilyl cyanide and a radical acceptor such as allylsulfone derivative, a difunctionalization of N-cyclobutylanilines has been realized through a multicomponent reaction fashion. The method was further expanded to the success difunctionalization of fused cyclopropylanilines. Structurally important α-cyano pyrrolidines were synthesized with the generation of a quaternary carbon center on the α positin of pyrrolidines.

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