Dynamic kinetic asymmetric ruthenium catalyst

Kejrwords Dynamic kinetic asymmetric transformation (DYKAT) Dynamic kinetic resolution (DKR) Hydrogenation Imine reduction Ketone reduction Mechanism of carbonyl reduction Mechanism of imine reduction Mechanism of dUiydrogen activation Ruthenium catalysis Shvo s catalyst Transfer hydrogenation... 

Ruthenium catalysts that contain Cl-MeO-BIPHEMP have been used in the asymmetric hydrogenation of P-keto esters (99% ee)126 and the dynamic kinetic resolution of substituted P-keto esters (Scheme 12.33).121 The asymmetric hydrogenation of methyl 3,3-dimethyl-2-oxobutyrate to the corresponding a-hydroxy ester has been reported with ruthenium catalyst, RuBr2[(-)-Cl-MeO-BIPHEMP] 2 (Scheme 12.34).121... 

Rhodium and ruthenium complexes of CHIRAPHOS are also useful for the asymmetric hydrogenation of p-keto esters. Dynamic kinetic resolution of racemic 2-acylamino-3-oxobutyrates was performed by hydrogenation using ((5,5)-CHIRAPHOS)RuBr2 (eq 3). The product yields and enantiomeric excesses were dependent upon solvent, ligand, and the ratio of substrate to catalyst. Under optimum conditions a 97 3 mixture of syn and anti p-hydroxy esters was formed, which was converted to o-threonine (85% ee) and D-allothreonine (99% ee) by hydrolysis and reaction with propylene oxide. 

Asymmetric transfer hydrogenation (ATH) reactions of 2-substituted a-alko gr-p-ketophosphonates (602) driven by dynamic kinetic resolution, afforded the corresponding 2-substituted a-alko gr-p-hydroxyphos-phonates (603) with excellent levels of diastereo- and enantioselectivity (Scheme 175). The reactions have been promoted by using chiral ruthenium catalyst (604) and a 0.2 1 mixture of formic acid and triethylamine as the hydrogen source and solvent. ... 

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