Some recent developments in free-radical additions to olefins and heteroarenes

Abstract : In the context of this thesis we studied several radical processes and in particular the addition of free-radicals onto unsaturated systems such as alkenes and aromatic heterocycles. We have thus shown the unique reactivity of carbamoyl radicals, issued from the decarboxylation of oxamic acids. Photocatalyzed “metal-free” carbamoylation of heterocycles was thus performed in the presence of an hypervalent iodine reagent, leading to -functionalized heteroaromatic bases, generally in good yields. The process was extended to oxamic acids prepared from homochiral amino acids and was shown to proceed without racemization.In the search for a functional group equivalent to an aldehyde and compatible with resident functional groups, we have devised a new free-radical olefin carbo-cyanation process, allowing the incorporation, on an olefin backbone, of a fragment bearing an electron-withdrawing group and a cyano group. Photochemical conditions have also been developed in order to avoid the use of costly initiators such as the di-tert-butyl hyponitrite (DTBHN). This key reaction was then used to construct, in only 4 steps, a bicyclic skeleton model for the alkaloid leuconoxine.Finally, in the last part of the thesis, we have described a straightforward synthesis of naphthalenones, bearing an all-carbon benzylic quaternary stereocenter. The reaction between a phenacyl halide and a substituted cyclopropene proceeds under photocatalysis using an iridium catalyst and visible light. A carbo-arylation of the cyclopropene is thus carried out leading to the corresponding cyclopropane, which is opened under the reaction conditions to afford the desired naphthalenone in moderate yields, with retention of the chirality of the starting homochiral cyclopropene.
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Submitted on : Tuesday, June 11, 2019 - 1:34:06 PM
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Ashique Hussain Jatoi. Some recent developments in free-radical additions to olefins and heteroarenes. Organic chemistry. Université de Bordeaux, 2019. English. ⟨NNT : 2019BORD0055⟩. ⟨tel-02152363⟩



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