Accelerated asymmetric transfer hydrogenation of aromatic ketones in water

Xiaofeng Wu , Xiaoguang Li , William Hems , Frank King and Jianliang Xiao*

*Liverpool Centre for Materials and Catalysis, Department of Chemistry, University of Liverpool, Liverpool, UK L69 7ZD, Email: j.xiaoliv.ac.uk

X. Wu, X. Li, W. Hems, F. King, J. Xiao, Org. Biomol. Chem., 2004, 2, 1818-1821.

DOI: 10.1039/b403627a

Abstract

Asymmetric transfer hydrogenation of various simple aromatic ketones by the Ru-TsDPEN catalyst was shown to be feasible in aqueous HCOONa without calling for any catalyst modification, furnishing ee's of up to 95% and significantly faster rates than in the HCOOH-NEt₃ azeotrope.

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Details

The study explores the accelerated asymmetric transfer hydrogenation of aromatic ketones using the Ru-TsDPEN catalyst in water, achieving high enantioselectivities (up to 95%) and faster reaction rates compared to the HCOOH–NEt₃ azeotrope. The catalyst, prepared by reacting TsDPEN with [RuCl₂(p-cymene)]₂ in water, showed full conversion of acetophenone to (R)-1-phenylethanol in 94% ee within 1 hour. The reaction in water was significantly faster and maintained high enantioselectivities across various ketones, although slightly lower than those achieved with the azeotrope. The study highlights water as a green solvent that enhances catalytic activity, selectivity, and productivity. The findings suggest that the reaction likely occurs in the substrate phase due to the biphasic nature of the system. The role of formate concentration and the use of deuterated reagents were also examined, indicating that C–H cleavage from the formato complex is rate-limiting. The research demonstrates the potential of the Ru-TsDPEN catalyst in water for efficient and environmentally friendly asymmetric synthesis of aromatic ketones.

On Water and in Air: Fast and Highly Chemoselective Transfer Hydrogenation of Aldehydes with Iridium Catalysts

X. Wu, J. Liu, X. Li, A. Zanotti-Gerosa, F. Hancock, D. Vinci, J. Ruan, J. Xiao, Angew. Chem. Int. Ed., 2006, 45, 6717-6722.

Asymmetric Transfer Hydrogenation in Water with a Supported Noyori-Ikariya Catalyst

X. Wu, X. Li, W. Chen, F. E. Hancock, F. King, J. Xiao, Org. Lett., 2004, 6, 3321-3324. DOI: 10.1021/ol0487175

Key Words

Transfer Hydrogenation, Reduction of Carbonyl Compounds, Ruthenium Catalysis, Formic acid

ID: J52-Y2004-680