Indiana University-Purdue University Indianapolis (IUPUI) / Aromatic rings are universal motifs in natural products, pharmaceuticals, agrochemicals,
and wide variety of organic materials. Aromatic halides are widely used as synthetic precursors
in all these applications. Therefore, tremendous effort has been devoted to activate aryl halides in
the past decades. The common methods to activate aryl halides require the use of transition-
metals either in the form of Grignard reagents or through the use of transition-metal catalysis.
Over the past decade, photoredox catalysis has attracted significant attention as a cogent tool to
develop greener synthetic processes and enable new molecular activation pathways under mild
conditions. The most common of these approaches uses a photoredox/nickel dual catalytic cycle.
While this technology has greatly expanded the toolbox of organic chemists, this method still
requires expensive rare-metal-based catalyts. Herein, we present a series of visible light-induced
methods that are transition-metal-free. These new base-promoted transformations and their
mechanistic work will be discussed in the following order:
We will first present our discovery that the dimsyl anion enables visible-light-promoted
charge transfer in cross-coupling reactions of aryl halides. This work was applied to the synthesis
of unsymmetrical diaryl chalcogenides. This method has a broad scope and functional group
tolerance. An electron-donor-acceptor (EDA) complex between a dimsyl anion and the aryl
halide is formed during the reaction and explains the observed aryl radical reactivity observed.
Then, a visible-light-induced borylation and phosphorylation of aryl halides under mild
conditions was developed. Inspired by the mechanistic breakthroughs observed in the previous
work. The mechanism of this reaction also involves an aryl radical that is presumed to be formed
also via an EDA complex. In other work, a photo-induced phosphonation of ArI using N,N-
diisopropylethylamine (DIPEA) and trialkyl phosphites was developed. This method uses very
mild conditions, which allowed the preparation a wide variety of functionalized aromatic
phosphonates derivatives, including natural products and medicinal compounds. Finally, a
photochemical amination of amides was developed via a C(sp 3 )–H bond functionalization
process under visible light irradiation. This reaction showed good functional group compatibility
without the use of external radical initiators, strong oxidants, or heat source. An EDA complex
between N-bromophthalimide and LiOtBu is formed during the reaction.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/27367 |
| Date | 12 1900 |
| Creators | Pan, Lei |
| Contributors | Laulhé, Sébastien, Long, Eric, O'Donnell, Martin J., Dai, Mingji |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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