Development of two organocatalytic photoredox transformations: The enantioselective cation radical Diels-Alder reaction and the anti-Markovnikov hydroamination of alkenes.

摘要

Herein we describe the development of two research projects within the field of organic photoredox catalysis. Both works involve the single electron oxidation of alkenes to generate cation radical intermediates which possess unique reactivity. The cation radical Diels-Alder reaction circumvents traditional electronic restraints on the substrates and allows for cycloaddition to occur between two electron-rich partners. We aimed to render this valuable reaction enantioselective by merging the fields of photoredox catalysis and chiral counteranion catalysis. The precedent for our research proposal and details of our findings are disclosed. We also employed cation radical intermediates for the development of an anti-Markovnikov hydroamination reaction catalyzed by an organic photoredox system. This transformation provides access to important pharmacological agents through the direct addition of amines to alkenes. The products are formed with complete anti-Markovnikov regioselectivity, a feature that is challenging to obtain without precious transition metals. We demonstrate 38 examples of the intra- and intermolecular anti-Markovnikov hydroamination reaction. Notably, the substrate scope includes trisubstituted aliphatic alkenes as well as heteroaromatic amines.