Catalytic performance of Noyori-Ikariya-type ruthenium complex with tethered syn-ULTAM ligand for the asymmetric transfer hydrogenation of ketones

The ruthenium complex of the tethered syn-ULTAM ligand, i.e. syn-3-(alpha-aminobenzyl)-benzo-gamma-sultam, has been evaluated for the asymmetric transfer hydrogenation (ATH) of a variety of ketones in formic acid/triethylamine mixture. Its performance was similar to the established Noyori-Ikariya-type catalysts for the reduction of benzofused cyclic ketones, but the enantioselectivity for the reduction of acetophenone was only moderate. The synULTAM-based catalyst was particularly efficient and enantioselective for ATH of the sterically demanding alpha,alpha-disubstituted ketones. Moreover, we report a divergent ATH of 2-phenyl-1,3-indandione to either cis-2phenyl-1-indanol, or cis,trans-2-phenyl-1,3-indandiol.