Highly Enantioselective Radical Cation [2 + 2] and [4 + 2] Cycloadditions by Chiral Iron(III) Photoredox Catalysis

• Published in: Journal of the American Chemical Society Vol. 145; no. 28; pp. 15054 - 15060
• Main Authors: Ohmura, Shuhei, Katagiri, Kei, Kato, Haruna, Horibe, Takahiro, Miyakawa, Sho, Hasegawa, Jun-ya, Ishihara, Kazuaki
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 19.07.2023; Amer Chemical Soc
• Subjects: catalytic activity; cations; Chemistry; Chemistry, Multidisciplinary; cycloaddition reactions; enantioselectivity; Physical Sciences; redox reactions; regioselectivity; Science & Technology; BRONSTED ACID; ANIONS; ANTI-MARKOVNIKOV HYDROETHERIFICATION; PHOTOCYCLOADDITION
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.3c04010

Radical cations show a unique reactivity that is fundamentally different from that of conventional cations and have thus attracted considerable attention as alternative cationic intermediates for novel types of organic reactions. However, asymmetric catalysis to promote enantioselective radical cation reactions remains a major challenge in contemporary organic synthesis. Here, we report that the judicious design of an ion pair consisting of a radical cation and a chiral counteranion induces an excellent level of enantioselectivity. This strategy was applied to enantio-, diastereo-, and regioselective [2 + 2] cycloadditions, as well as enantio-, diastereo-, and regioselective [4 + 2] cycloadditions, by using chiral iron­(III) photoredox catalysis. We anticipate that this strategy has the potential to expand the use of several mature chiral anions to develop numerous unprecedented enantioselective radical cation reactions.