trans-Diastereoselective Ru(II)-Catalyzed Asymmetric Transfer Hydrogenation of α-Acetamido Benzocyclic Ketones via Dynamic Kinetic Resolution

A highly efficient enantio- and diastereoselective catalyzed asymmetric transfer hydrogenation via dynamic kinetic resolution (DKR-ATH) of alpha,beta-dehydro-alpha-acetamido and alpha-acetamido benzocyclic ketones to ent-trans-beta-amido alcohols is disclosed employing a new ansa-Ru(II) complex of an enantiomerically pure syn-N,N-ligand, i.e. ent-syn-ULTAM(CH2)(3)Ph. DFT calculations of the transition state structures revealed an atypical two-pronged substrate attractive stabilization engaging the commonly encountered CH/pi electrostatic interaction and a new additional O=S=O center dot center dot center dot HNAc H-bond hence favoring the trans-configured products.