Asymmetric transfer hydrogenation chiral alcohol production

Asymmetric Transfer Hydrogenation of Ketones. The first reports on asymmetric transfer hydrogenation (ATH) reactions catalyzed by chiral metallic compounds were published at the end of the seventies. Prochiral ketones were reduced using alcohols as the hydrogen source, and Ru (274,275) or Ir (276) complexes were used as catalysts. Since then, many chiral catalytic systems for homogeneous ATH of ketones, imines, and olefins have been developed (37,38,256,257,277-289). The catalytic systems are usually based on ruthenium, rhodium, or iridium, and the ATH of aryl ketones is by far the most studied. Because of the reversibility of this reaction, at high conversions, a gradual erosion of the ee of the product has been frequently reported. An azeotropic 5 2 mixture of formic acid/triethylamine can be used to overcome this limitation. 

Enantioselective transfer hydrogenation (from propan-2-ol) of some ketones catalysed by iridium(i) complexes with chiral Schifl-base ligands has been reported, giving product alcohol of up to 33% e.e. with propiophenone as substrate. Other new reductive routes to chiral secondary alcohols involve the asymmetric hydrogenation of enol phosphinates (21) catalysed by chiral ferrocenyl-rhodium... 

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