Enantioselective\nTransfer Hydrogenation of α‑Methoxyimino-β-keto\nEsters

α-Methoxyimino-β-keto esters are reported\nto undergo\nhighly enantioselective catalytic transfer hydrogenation using the\nNoyori–Ikariya complex RuCl(<i>p</i>-cymene)[(<i>S</i>,<i>S</i>)-Ts-DPEN] in a mixture of formic acid–triethylamine\nand dimethylformamide at 25 °C. The experimental study performed\non over 25 substrates combined with computational analysis revealed\nthat a <i>Z</i>-configured methoxyimino group positioned\nalpha to a ketone carbonyl leads to higher reactivity and mostly excellent\nenantioselectivity within this substrate class. Density functional\ntheory calculations of competing transition states were used in rationalizing\nthe origins of enantioselectivity and the possible role of the methoxyimino\ngroup in the reaction outcome.