Organocatalytic Enantioselective Protonation for Photoreduction of Activated Ketones and Ketimines Induced by Visible Light

• Published in: Angewandte Chemie International Edition Vol. 56; no. 44; pp. 13842 - 13846
• Main Authors: Lin, Lu, Bai, Xiangbin, Ye, Xinyi, Zhao, Xiaowei, Tan, Choon‐Hong, Jiang, Zhiyong
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 23-10-2017
• Edition: International ed. in English
• Subjects: asymmetric photoredox catalysis; Catalysis; cooperative catalysis; Diketones; Enantiomers; Imines; Irradiation; Ketones; Light irradiation; organocatalysis; Photochemistry; Photoreduction; Protonation; organocatalysis; protonation; asymmetric photoredox catalysis; photoreduction; cooperative catalysis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201707899

The first catalytic asymmetric photoreduction of 1,2‐diketones and α‐keto ketimines under visible light irradiation is reported. A transition‐metal‐free synergistic catalysis platform harnessing dicyanopyrazine‐derived chromophore (DPZ) as the photoredox catalyst and a non‐covalent chiral organocatalyst is effective for these transformations. With the flexible use of a chiral Brønsted acid or base in H+ transfer interchange to control the elusive enantioselective protonation, a variety of chiral α‐hydroxy ketones and α‐amino ketones were obtained with high yields and enantioselectivities.
Enantioselective protonation: The first catalytic asymmetric photoreduction of 1,2‐diketones and α‐keto ketimines under visible light irradiation relies on a transition‐metal‐free cooperative catalysis platform that harnesses dicyanopyrazine‐derived chromophore (DPZ) as the photoredox catalyst and a noncovalent chiral organocatalyst. A variety of chiral α‐hydroxy ketones and α‐amino ketones was obtained with high yields and enantioselectivities.