Tang W, Johnston S, Li C, Iggo JA, Bacsa J, Xiao J * University of Liverpool, UK
Cooperative Catalysis: Combining an Achiral Metal Catalyst with a Chiral Brønsted Acid Enables Highly Enantioselective Hydrogenation of Imines.
Chem. Eur. J. 2013;
19: 14187-14193
Key words
iridium - Brønsted acid - cooperative catalysis
Significance
Optically active amines are common in many fine chemicals, agrochemicals, and pharmaceuticals. The authors report a cooperative metal-organo catalytic system utilizing a chiral Brønsted acid and an achiral iridium catalyst (see below for a Review on transfer hydrogenation).
Review
C. Zheng, S.-L. You Chem. Soc. Rev. 2012, 41, 2498–2518.
Comment
The authors have reported the cooperative use of a chiral iridium catalyst with a chiral phosphoric acid in the asymmetric hydrogenation of acyclic imines with H2 (J. Am. Chem. Soc. 2008, 130, 14450). Here, they report an achiral iridium catalyst with a chiral phosphoric acid in a similar reaction. Alkyl imines, which are known to be difficult substrates for asymmetric hydrogenation, were shown to be excellent substrates in this system, giving enantioselectivities up to 97%.
