Visible-Light Photoredox-Catalysed Radical Cascade Reactions

The research presented in this thesis details several novel radical cascade transformations under copper-catalysis or visible-light photoredox-catalysis.
The synthesis of [1,2]-annulated indoles from ene-ynamides via a radical triggered
fragmentary cyclisation cascade under copper-catalysis or photoredox-catalysis is described. This reaction proceeds through a radical addition, radical cyclisation, desulfonylative aryl migration, and site-selective C(sp2)-N cyclisation sequence. This work presents an example of a radical Smiles rearrangement process followed by aza-Nazarov type cyclisation, which enables the selective incorporation of the electron-rich aryl ring into the indole motif regardless of its original position.
The second part of thesis explores the synthesis of α-arylated carboxylic acids, esters, and amides from consecutive defluorination of α-trifluoromethyl alkenes in the presence of potassium alkyltrifluoroborates, water, and nitrogen/oxygen nucleophiles under
organophotoredox-catalysed conditions. The utility of this method has been expanded
through several product transformations. Mechanistic studies show that this metal-free
reaction consists of a defluorinative alkylation, defluorinative hydroxylation, and defluorinative amination/hydroxylation cascade.
Finally, the modular synthesis of α-tertiary primary amines using α-aryl vinyl azides, redoxactive N-(hydroxy)phthalimide ester, and cyanoarenes under visible-light conditions is described. This strategy shows excellent functional group compatibility and allows the straightforward synthesis of 2,2-diaryl tetrahydroquinolines and 1,2-amino alcohols. The mechanistic studies support two parallel reductive photocatalytic cycles allowing for the denitrogenative alkylarylation of vinyl azides through decarboxylative radical addition followed by hetero-radical cross-coupling between α-amino alkyl radicals and aryl radical anions.

本论文中的研究详细介绍了铜催化或可见光光氧化还原催化下的几种新型自由基串联反应。
第一部分介绍了在铜催化或光氧化还原催化下通过自由基串联反应从炔酰胺合成[1,2]-环吲哚的反应。该反应通过自由基加成、自由基环化、脱磺酰基芳基迁移和位点选择性 C(sp2)-N 环化顺序进行。这项工作展示了一个自由基Smiles重排以及aza-Nazarov型环化的例子，这使得富电子芳基环选择性地并入吲哚中，而不管其原始位置如何。
论文的第二部分探讨了在烷基三氟硼酸钾、水和氮/氧亲核试剂存在下，通过在有机光氧化还原催化条件下由α-三氟甲基烯烃连续脱氟合成α-芳基羧酸、酯和酰胺。该方法的实用性通过产物的衍生化得到了扩展。机理研究表明，这种无金属反应由脱氟烷基化、脱氟羟基化和脱氟胺化/羟基化级联组成。
最后，本文描述了在可见光条件下使用α-芳基乙烯基叠氮化物、氧化还原活性N-(羟基)邻苯二甲酰亚胺酯和氰基芳烃模块化合成α-叔伯胺。该策略显示出出色的官能团相容性，可直接合成 2,2-二芳基四氢喹啉和 1,2-氨基醇。机理研究支持两个平行的还原光催化循环，通过自由基加成及α-氨基烷基自由基和芳基自由基阴离子之间的自由基交叉偶联来实现乙烯基叠氮化物的脱氮烷基氨基化。

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