Hydrogenation of C=O bonds

The asymmetric hydrogenation of C—O bonds have now been achieved in optical yields up to 95%, rivalling the performance of alkenes. Here also, rhodium complexes have been used almost exclusively, but some success has been obtained with cobalt catalysts. Using [Co(HDMG)2] in presence of optically active bases, benzil could be reduced to benzoin (equation 54) in an optical yield of 78%. Quinine or quinidine were the chiral bases employed. The best optical yields were obtained with quinine (60). It was found that when benzylamine was also present, the rate of hydrogenation was greatly enhanced without any decrease in the optical yield.276... 

Despite the lower chemisorption capacity after a HTR pretreatment, this catalyst was 45% more active than after a LTR pretreatment and had a TOF that was 7 times higher. These higher activities and TOFs in reactions involving the hydrogenation of C-O bonds has been attributed to the creation of new sites at the metal-titania interface as a consequence of the removal of surface oxygen atoms from the Ti02 lattice [38,39]. After assimilating all the spectroscopic and kinetic data, the latter of which are shown in... 

---