Chiral Phosphoric Acid Catalyzed Transfer Hydrogenation of Ketimines
A. Henseler, M. Kato, K. Mori, T. Akiyama*
Gakushuin University, Tokyo, Japan
20 September 2011 (online)
Akiyama and co-workers report an asymmetric phosphoric acid catalyzed synthesis of aromatic and heteroaromatic trifluoromethylated amines. To show the utility of this reaction, the authors carried out the synthesis of a perfluoroalkylated analogue of the bioactive compound NPS R-568. Benzothiazoline was used as a hydride source, and it shows stronger reactivity compared to the Hantzsch ester, which is commonly used as a transfer hydrogenation agent. Also, by employing a deuterated benzothiazoline in the reaction, the authors were able to enantioselectively incorporate deuterium into the products and at the same time provide support for a hydride mechanism in the transfer hydrogenation of ketimines with benzothiazoline.