DYKAT diols, dynamic kinetic

The Shvo catalyst 1 was successfully used in the transfer hydrogenation of 1,3-diones to the corresponding 1,3-diols with isopropanol as the hydrogen donor (2) [36, 37], This reaction is synthetically useful for the reduction of cyclic diones since reduction of these diketones by LiAlIli preferentially gives the aUyUc alcohol [36]. Also piperidine-3,5-diones were efficiently reduced to the corresptMiding diols by isopropanol using 1 as catalyst [37], and these diols were subsequently used in dynamic kinetic asymmetric transformatimis (DYKATs) to provide stereodefined 3,5-disubstituted piperidines [36, 37],... 

The enzyme-catalyzed kinetic asymmetric transformation (KAT) of a diastereomeric 1 1 syn anti mixture is limited to a maximum theoretical yield of 25% of one enantiomer. This important drawback has been overcome by the combination of the actions of a ruthenium complex and a lipase in a dynamic kinetic asymmetric transformation (DYKAT), the desymmetrization of racemic or diastereomeric mixtures involving interconverting diastereomeric intermediates, implying different equilibration rates of the stereoisomers. Thus, this strategy allows the preparation of optically active diols, widely employed in organic and medicinal chemistry, as they are an important source of chiral auxiliaries and ligands and they can be easily employed as precursors of much other functionality. 

Martin-Matute, B., Edin, M., and Backvall, J.-E. (2006). Highly efficient synthesis of enan-tiopure diacetylated C-2-symmetric diols by ruthenium- and enzyme-catalyzed dynamic kinetic asymmetric transformation (DYKAT). Chem. Eur.., 12,6053-6061. 

Fig. 8.33 DYKAT of 1,3-diols via lipase-catalyzed acyl-transfer in combination with Ru-catalyzed epimerization of hydroxyl groups. G=chiral carbon, convertible for equilibration and acyl migration, but not for the irreversible step H=chiral carbon, convertible for equilibration, acyl migration and the irreversible step l=chiral carbon, convertible for acyl migration, stable chirality. (From J. Steinreiber, K. Faber, H. Griengl, De-racemization of enantiomers versus de-epimerization of diastereomers-chssification of dynamic kinetic asymmetric transformations (DYKAT), Chemistry 14 (2(X)8), 8060. Copyright 2008 Wiley).

---