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Catalyst-Controlled Radical Reactions

 

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The concept behind our research is the development of so-called catalyst-controlled radical reactions. Here, the catalyst stays coordinated to the substrate during the radical coupling process and thus enables excellent control of the chemo-, regio-, stereo-, and even enantioselectivity. We are interested in employing this concept in the design of new reactions and catalysts that enable unprecedented coupling reactions. Furthermore, it is our goal to show the feasibility of these radical processes for the synthesis of natural and synthetic targets. Since a detailed understanding of the catalyst-controlled processes is crucial for the advancement towards new and improved reactions, we investigate the underlying mechanisms as well. 

 

Reductive Umpolung Reactions

Titanium(III)-catalysis provides exceptional control over radical-based catalyst-controlled C-C coupling reactions starting from carbonyls, epoxides and related precursors. This way, pinacol-type dimerizations of aldehydes and related umpolung reactions were realized in exceptionally high diastereoselectivities. It is our goal to expand the reductive umpolung technology towards selective cross-coupling reactions. Until today, we have developed a series of titanium(III)-catalyzed couplings that led to 1,2- 1,4- and 1,6-difunctionalized products starting from readily available ketones, nitriles or Michael-acceptors as coupling partners. These radical couplings are complementary to classical cross-coupling reactions. A striking feature is that no pre-metallation is required. Instead, simple carbonyls, nitriles or activated alkenes serve as coupling partners. A summary of the product scope and the respective reductive C-C bond formations achieved by us to date is given below. For more details, see our publications.

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